Guess that's the Star fleet training? And Guinan is of a race we know very little about, so we don't know how they process things when they're that young. She did enjoy jumping on the bed. Plus, the way El-Aureans age, who knows how old they'd be when looking that young. She could be 200 years old there for all we know lol. In Picard she was played by a younger actress (I get and support why they wouldn't use Whoopie, obviously, but the actress they used looked younger than Whoopie was during TNG). Yes, it's before the events of TNG, but it's also after when she was hanging out with Samuel Clements, where they still used Whoopie, and she appears the same age as during TNG. They didn't use a younger actor there, because the implication was that her body hadn't really aged in all that time. That being said I'll get slightly tangential and pedantic and say it makes no sense that they used an actress younger than Whoopie was during filming of TNG, as it makes it so she appears to have gotten younger between hanging out with Mark Twain in TNG, and the flashback in Picard.