Right Will. It is about sex, any unclothed female simply is, no matter our intellectualization. Given that, Mortensen's naked ladies are good schtick-sex but for the most part lack heart and soul and respect and are only patently humorous. I'm no student of his stuff but what I see I yawn at.
As the universe knows, Weston was a recorder of everything including dead itinerants and totally natural, completely naked girl friends. I personally find his riveting Mexican-era Heads of Nahui Olín and Manuel Hernández Galván absolutely beyond magnificent. And when I observe the boiling emotion in those two faces his unclothed females appear strangely unsensual, so dutifully respected there is no 'heat' at all - I mean he was so connected to these women yet there is no warmth, just perfect recordings of Form. I find the neutrality amazing!
The difference behind the two talented men to me is not in their pictures of female nakedness but in their means to the end: one was a showman who too-used female nakedness, the other was an artist who too-respected naked females. Neither ever captured the IT other well-known and not-known photographers have.