Seems to me what your grandmother was talking about is gendered attributes, which suggests the biological sex of the parent is not as important as being loved and invested in, in a prep for the world sense.

This tracks for me.

I've known plenty of guys who had both parents at home who were absolute wrecks, and others who had a single mom with very little support who were very well rounded.

You do need both, or rather, you need ALL the human traits that have been divided by gender through design.

This also suggests that the nuclear family, popularized after WWII is bad for children and we should get back to more alloparenting with extended family.