Maybe pederasity isn't the same as pederasty.

Sometimes pederasty is also used as a shorthand for 'age-discordant homosexuality', meaning a type of institutionalized homosexuality where roles (and not just in the bedroom) are determined by age. Typically found more in state-level societies, but it does occur in some pre-state societies as well. (I'm thinking New Guinea here.)

Most homosexuality, cross-culturally, can be divided into that, the gender system (feminine men or masculine women), or adolescent fun. The 'gay' system, e.g. two members of the same sex approximately the same age and who after they're initiated (a.k.a. coming out) will never engage in another heterosexual act, is actually a novelty.