Something seems odd about the supposition and their opening data set with older, childless women - do women that are childless and infertile from an earlier age

Something seems odd about the supposition and their opening data set with older, childless women - do women that are childless and infertile from an earlier age feel similarly? Why not flip this around to comparing how men with vasectomies at earlier ages feel decades later? Paternal instinct and maternal instinct overlap somewhat I presume but it’s not clear what the differences are I suspect.