This particular fact about Brock might just be the most immediately undeniable evidence of the fact that he's gone entirely too far in his obsession with random women he encounters throughout the series. Brock admits to the fact that he keeps a little blue book in his pocket at all times eventually, which might be assumed to be perhaps a journal or an innocent notebook, but no. It's a list of literally every woman he's ever met or interacted with, kept entirely up to date, all the time. That's certified crazy person behavior.