Yes it is. As a form of marketing to make people who otherwise don't play RPGs take notice and hook them. Hence also the prominently advertised bear sex scene.
Larian used sex both to hook in new customers segments and to distract from BG3 just offering average industry standard fare and often even below that. Sex sells, a good or at least functioning story sadly does not as the success and hype of BG3 proves. Idiocracy here we come.
And yes, you also rightly noticed that BG3s companions suffer a lot because all of them have to be (very) sexual which limits the type of possible (origin) companions and that companions in other RPGs, for example Kingmaker and Wrath, are much better. And not only does BG3 oversexualisation limit the type of companions, the companions that exist are also modeled primarily to fulfil sexual fantasies. Just play a romantic/sexual visual novel and you will see a huge overlap between the character types in it and BG3. The tsundere, the shy girl, the bully with a soft core, ect.
