Poise and sophistication is something that often comes with age regardless of gender.

Relative poise and sophistication. Nobody exists in a vacuum, and while yes I do agree that people generally progress and refine themselves as they age, there are hundreds of other factors that I would argue are vastly more relevant than age. It's not hard to find a 20 year old from a nurturing environment or conversely a 20 year old who survived difficult and grounding circumstances either of which may display vastly more sophistication and poise than a spoiled 60 year old raised in comfort and wealth who never had to challenge any of their expectations.

While some trend might exist between the two things, a) I think it's wildly overblown, b) it's nowhere near absolute enough to establish rules based upon it, and c) regardless it's an aside from what you claim to be after anyway. If you want a partner with sophistication and poise, then seek one with those qualities, don't just project them onto him/her/them because you assume they should have them based on age. If you've got a craving for apple you shouldn't pick up a pomegranate just because you know the food you like is colored red.