The RTC gender-related growth disparity that I have mentioned is only based on my 10 RTCs that I have had for not that long, 7 of them only for 2 years, and they are all rescues but one.
I don't recall reading this growth info anywhere else. That makes me assume that my tentative observation may be wrong or my gender assignment may be too. Sexing RTC is said to be unknown in many sources, which makes my conclusions double unreliable until more verification is available.
From what I could see, the females have narrower and more sloping head shape versus males and are invariably smaller among my 10 fish relative to males. The males' heads are flatter and wider, typical of catfish species in general (but not all inclusive). I don't really see in my 10 anything in between - it's either one type of head or the other. And it coincides with size disparity, which is a bit trickier as one of my males is a finicky feeder, so it's lagging behind.
All in all, this gender distinction is more or less obvious to my eye, if proven in the future to be correct with more data.
As for other catfish species, females can and often do exceed males either in mass or in length or both. So, I'm not aware of how to generalize that aspect over all or most catfish species... or only over those that grow large, which is our interest.