I co-own third party repair shops (we are not Apple certified since we do more complex repairs) and the screens for the 6S-XS have 3D Touch on them even if they’re not replaced by Apple.
I will say this, in 50,000+ 3D Touch iPhone screen repairs (conservative estimate) I don’t recall any complaints about non-working 3D Touch. I think probably 0.1% of iPhone users even knew it existed.