Much of his work was published in Condé Nast's Vogue Magazine's French, British, American and German versions. Examples are shown below along with other illustrations whose sources were not clear from Internet sources.
It seems that fashion illustration, along with its subject matter, follows its own set of fashions. 1920s illustrations tended to simplify human figures and clothing, creating flattening to various degrees depending on the artist or perhaps the art director. In the 1930s fashion changed to free-style wash drawings, this persisting into the 1950s and beyond. There also seem to have been some national differences, as Mourgue's 1920s cover illustration for German Vogue are more simplified than those he did for other editions.
In two words, Mourgue was both fashionable and versatile.
Some of his comparatively early work was for a men's magazine. Doesn't look like that guy on the right spent much time in the trenches around Verdun.
Mourgue's illustrations sometimes used more shape modeling than was common at the time.
Not a fashion illustration.
An example of his simplified German style.
Mourgue traveled to the USA a lot, according to the link above. The background of this illustration seems to be a greatly enlarged New York Central Park lake.
All is flatly done save the car's steering wheel.
New decade, new fashion trend.
Original publication illustration, probably for French Vogue.
The new fashion illustration style.