You're probably right- these ideas are still pretty new as far as the general public is concerned so they're still figuring shit out and it makes sense that the folks who practice would default to technical-sounding terms in an attempt to legitimize it maybe? I just kinda feel like there's a key difference between legitimizing and normalizing and more casual, affectionate terms would help w/ the normalization part.
Also TIL (via Wiki):
"Compersion is a positive feeling which a person may sometimes experience when their partner is happily involved with somebody else, in contrast to jealousy.
New relationship energy or NRE, is the surge of emotional and sexual openness and excitement usually experienced in relatively new relationships, with recognition of the contrast with the more settled emotional and erotic connections experienced later in the same relationship, or in other ongoing relationships at the same time. "