I think the strongest bias in this case is favoring advisors over the students who do the work, even if they get first authorship.

For example, the Alex of AlexNet [1] fame would be Alex Krizhevsky, if he were actually famous. He doesn't have a Wikipedia page, but his advisor Geoffrey Hinton does (and is famous for the AlexNet breakthrough).

[1] https://en.wikipedia.org/wiki/AlexNet