But that would only make sense if the younger people think that anyone can choose their own reproductive role
It could be they mean reproductive role in a larger sense - including things like being primary care giver, or not having kids at all. It's still a stretch but I think a lot of young women who haven't had kids think all the stuff after pushing out the baby is up for grabs. (And TBF I've heard a fair few older feminists make the same claim.)
I have to say, I think part of the reason this disconnect has happened at all is that the gender critical stance, this idea that we could have a society without gender, is really pie in the sky, it can never happen and probably would not be very nice if it did. Our sexual realities always assert themselves in ways that are not just completely directly related to reproduction. In any pre-modern society the hole pattern of daily life for the whole culture will be shaped by them, our experiences as a group are shaped by our sexed bodies, our relation to other people is impacted by our awareness of their sexual role compared to our own, sometimes in a very positive way, sometimes very negative, sometimes is a rather complicated way. It becomes reflected in our laws. It inserts itself into our cultural expressions, art, literature, myth, our perceptions of nature.
When we think we could somehow get rid of all of this, I think it creates a sort of blind spot, or paradox. We know we have this sense, but it's as if people think our cultural expression of sexual dimorphism is a random and so could be rearranged in any which way. Not just switching something like pink to boys or blue to girls, or parenting roles between the sexes, or whatever - instead the expressions are still there but they are still there but are like points on a graph that has no labels.
I'm not entirely expressing myself well, but I guess I mean that I think if we acknowledged that gender is always going to exist, and to some extent most people like it to, we could much more easily talk about ways in which it might be problematic and deal with those. There will always be masculinity and femininity because we will always know and think of ourselves in all the ways that our sexual bodies interface with the world and our experience and relation to the other. But we don't want those to be prisons for people.