Has anyone, based on great performance, ever been awarded a higher degree than the one they enrolled for?
Although a bit old, there's the case of Luzin's Master's thesis: . . . he completed his thesis The integral and trigonometric series which he submitted in 1915. After his oral examination he was awarded a doctorate, despite having submitted his thesis for the Master's Degree. In fact, even for a Ph.D. thesis, Luzin's is one of the strongest ever written in mathematics --- in my opinion easily in the top 20 (and probably in the top 10) of all-time Ph.D. theses in mathematics for its influence on later developments.

This appears to be the published version of Luzin's thesis, which is 242 pages and in Russian, with the table of contents on pp. 241-242. For references to it, this search and this other search seem to work the best. I didn't get many hits for the title's French translation, by the way.