Milhouse, if anyone attended the University because of enrollment in Hildesheimer, their attendance would be recorded. The Rebbe and Rav Hutner, who knew each other and then parted company 20+ years later, audited some classes; they were not students.
the Rebbe, who may have similarly audited a few classes at the Sorbonne was an average student at a second/third rate technical school in Paris. given his limited background, that should not be diminished