I do get what you're saying, and I think the ability to opt out of romance should be an option, but you realise that this is the game where we were promised fully rendered and animated sex scenes by the dev team? The over-sexed nature of our companions is 100% intended. No amount of explanation for their actions seems totally believable, because it's not meant to be, the characters aren't that deep.

Considering how easy it was to accidentally trip into romance in DOS2 just by not being an arsehole to everyone around you, and the overly-detailed descriptions of the various sexual encounters you can have throughout that game, making your companions a pack of horny bastards is on-brand for Larian. But, having said that, I've played multiple crpgs where the romance is initiated by the npc. Sometimes it's well written and built up over many encounters, other times it's Casavir the adulterer ambushing you on a castle wall the night before a siege, declaring his undying love for you and inviting you to smash, because... *checks notes* you're female and not a murderhobo. Truly a paladin of high standards.