I don't know, but my best guess is widely available child care even for very young children and full-time employment for both men and women being the norm. Much easier to be friends with the other sex if they're not stuck at home with the kids.

Not sure about the DDR but I know the Soviets had a slightly higher level of COED sports and whatnot. Also I think the Soviet scouts equivalent was also COED, if that bled into the DDR it's possible that wouldve had knock on effects up to now.

Also I'm using DDR because GDR sounds weird to me and I grew up around folks who used the German name for some fucken reason.

a shitty economy and living conditions that forced both sexes to work to survive. also a lack of income inequality.

there is kind of an inverse, in inequal societies there tends to be a greater separation of the sexes.