When it comes to Debbie and Jenny, it's indeed true that DC never intended to add a threesome for them, even before Patreon started to ban incest. In his mind they are just too different and simply don't have a real reason or the relationship to have threesome with MC. He basically always argued that it would be be too much work to write a credible story that suits both of them. Then again, both of them (will) have threesomes with other characters, so I don't think it's actually that bad. But sure, for those who really, really like incest it's a problem.