Only modern _homosexuality,_ though, is burdened with the requirement to prove that its historical antecedents were somehow more egalitarian than the norm for its time.
Yes, that's pretty much what I said. Hence also the historical focus on socially sanctioning heterosexual sex via marriage, and on the family's role in carefully vetting prospective marriage partners. It clearly didn't go as far as modern "consent culture" towards solving the issue, but it was a rough attempt.
Marriage and prison bitch have very different connotations to us. To an alien...these are all in the sphere of coupling relationships. Ultimately, a 4th century peasant marriage, 19th century marriage, a 1950s American marriage and a modern, suburban gay marriage are all different from eachother... there's a common thread though.
The semantics tend to become the discussion.
(OP's article does attempt to reframe the typical practices of the time and make them "fit" the modern egalitarian view, but note how even in their own account it's always the older, more dominant member of the pairing who is said to "love" and "care" for his younger and more submissive partner. This is clearly the same sort of highly skewed arrangement that is well known from ancient Mediterranean cultures.)