Kathryn made Mike smarter because it's demeaning to have a sexidiot.
It means that she likes sex less than than pondering what people are talking about who she is having sex with.
She needed noble reasons to act like a sexed up milf which weren't there in the beginning.
If she spreads her legs for a mere "bartender" it explains how little she values herself to slide down the social order and evolutionary ladder to dig her nails into the back of a man who probably can't even spell "Trinity College" gods forbid he was going there.
(Notice how kathryn wanted a student, and not someone with a degree, because although she didn't want to be seen as slumming it with a piece of rough, she also didn't want to be out shone by a caveman or even an irishman, I'm not quite sure where her racism lies here, but it's safe to cover all her bases.)
Janeway had to justify the dew building up in her fleet issue underwear by making sure that her reptile brain which was already overclocking her pants for this complete disappointment and loser. She had the technology to make him civilized and magnificent enough for her HIGH standards. Sure Kathy made Michael three centimetres taller, because that's really important in a boyfriend but she had to invent and postdate a host of excuses and justifications like education and personality for why she already wanted his starting-character superficiality to rock her world before he levelled up... And pretend that that's who he always was, and why she wanted him in the first place for the qualities she hadn't yet wedged into him.
Normal day at the office really.