That way of using the term class is alien to its use in historical materialism/marxism. In the US its largely been a means to dilute an understanding of class politics and mystify workers with abstract definitions. The term middle class among Marxists has largely been used as a means to talk about the intelligensia, portions of the petit-bourgeoisie, the managerial and professional strata, etc (for example, Bela Kun's article "Marx And The Middle Classes"          https://www.marxists.org/archive/kun-bela/1918/05/04.htm    ). In the US, the term "middle class" means the working class- particularly better paid workers, or better educated workers- and things like home ownership, good benefits, etc that come along with it. It's a tool used to confuse and mystify American workers from identifying as workers first- thinking they have a dog in the race with the bourgeois parties and their elections.

Quote:

From what I have read so far, most of the "third world" Marxist/Stalinist/Maoist movements have been those of the middle class.

Tony Cliff's article 'Deflected Permanent Revolution' discusses this- the absence of the proletariat in the so-called 'Communist Party's, and the professional strata, the intelligensia, etc taking the reigns of the national revolutions.

Quote:

The industrial working class played no role whatsoever in the victory of Mao. Even the social composition of the Chinese Communist Party was completely non-working class. Mao’s rise in the party coincided with its transformation from a working class party. Towards the end of 1926 at least 66 per cent of the membership were workers, another 22 per cent intellectuals and only 5 per cent peasants.  By November 1928, the percentage of workers had fallen by more than four-fifths, and an official report admitted that the party “did not have a single healthy party nucleus among the industrial workers”. The party admitted that workers comprised only 10 per cent of the membership in 1928, three per cent in 1929, 2.5 per cent in March 1930, 1.6 per cent in September of the same year., and virtually nothing at the end of it.  From then and until Mao’s final victory the party had no industrial workers to speak of.

For a number of years the party was confined to insurgent peasant movements deep in the provinces of central China, where it established a Chinese Soviet Republic; later, after a military defeat in the central provinces (1934), it moved to northern Shensi, in the north-west. In both these areas there was no industrial working class to speak of. A Comintern organ was not exaggerating when it wrote that “the Border Region is socially and economically one of the most backward regions of China.”  Chu Teh repeated: “The regions under the direction of the Communists are the most backward economically in the whole country ...”  Not one real town came under the control of the Communists until a couple of years before the establishment of the Chinese People’s Republic.

So unimportant were workers in Communist Party strategy during the period of Mao’s rise to power that the party did not find it necessary to convene a National Congress of Trade Unions for 19 years after the one held in 1929. Nor did it bother to seek workers’ support, as witnessed in its declaration that it did not intend to maintain any party organisation in the Kuomintang-controlled areas during the crucial years 1937-45.  When, in December 1937, the Kuomintang government decreed the death penalty for workers who went on strike or even agitated for a strike while the war was in progress, a Communist Party spokesman told an interviewer that the party was “fully satisfied” with that government’s conduct of the war. Even after the outbreak of civil war between the Communist Party and the Kuomintang, hardly any Communist Party organisations existed in the Kuomintang areas, which included all the industrial centres in the country.

Mao’s conquest of the towns revealed more than anything else the Communist Party’s complete divorce from the industrial working class. Communist leaders did their best to prevent any workers’ uprisings in the towns on the eve of their being taken. Before the fall of Tientsin and Peking, for example, General Lin Piao, commander of the front, issued a proclamation calling on people:

to maintain order and continue in their present occupations. Kuomintang officials or police personnel of provincial, city, country or other level of government institution; district, town, village, or pao chia personnel ... are enjoined to remain at their posts ...

At the time of the crossing of the Yangtze River, before the great cities of Central and South China (Shanghai, Hankow, Canton) fell to them, Mao and Chu Teh again issued a special proclamation stating among other things:

It is hoped that workers and employees in all trades will continue to work and that business will operate as usual ... officials of the Kuomintang Central, Provincial, Municipal or County Governments of various levels, or delegates of the “National Assembly”, members of the Legislative and Control Yuans or People’s Political Council members, police personnel and heads of Pao Chia organisations ... are to stay at their posts, obey the orders of the People’s Liberation Army and People’s Government. The working class obliged and remained inert. A report from Nanking on 22 April 1949, two days before the People’s Liberation Army occupied it, described the situation in this way:

Nanking’s populace is showing no signs of excitement. Curious crowds were seen this morning to gather at the river wall to watch the gun duel on the opposite side of the river. Business is going on as usual. Some shops are closed, but it is due to lack of business ... Movie houses are still showing to packed houses.

https://www.marxists.org/archive/cliff/works/1963/xx/permrev.htm