There is a bit to unpack here.
A trend? Perhaps. Although like DAZ, Blender, etc. rendering was a "trend"...until it wasn't. That is, as technology progresses, developers see it as a tool to bring their creations to life and if there is enough interest in the outcomes it will cease to be a "trend" and just become a means to create. We need to think beyond the smaller corner of F95 (and other Adult VN sites) and realize that AI is here to stay and every day there are new AI Image and Story Generation websites and applications popping up. The personal preferences of an individual has very little impact on whether the us AI for image generation will stay or go away. It comes down to exactly that - whether an individual likes AI art or not doesn't matter beyond that individual. Plainly put, people should look at it as a choice. You like AI art? Fine. You don't like AI art? Fine. It is all a matter of personal taste and aesthetics.
I will admit the Phone/Texting VNs are most likely a trend and, if I am being honest, I am surprised it hasn't happened sooner. As sexting, AI, and the use of Social Media has been on an extremely fast growth pace since 2012, the old adage applies: "Art imitates art" I believe you will see even more of them as time goes on...until the next trend pops up.
Regarding NTR/NTS...what's the question here? This, like any other fetish/kink, is strictly a matter of personal preference. You like it? Fine. You don't like it? Fine. As an example: When I log into F95 and enter the "Latest Updates" page, a good 80% of the Game/VN threads are greyed out as ignored for me; I know what I like and what I don't like. If the question was about the number of NTR/NTS Phone/Text based VNs that are beign produced, I don't see that there are more NTR/NTS VNs that are being produced. Rather there are a larger number being produced as Phone/Text based VNs using AI - the theme is irrelevant.