I haven’t looked too much into that paper, but yeah, it could be that at smaller scales you are just perceiving the friction.
But just from personal experience, I am pretty confident that at least in the 10μm-100μm range humans have high fidelity tactile perception, and are able to distinguish various patterns and not just friction.
It is unclear from my reading of the paper that the result is anything beyond “fine waves cause friction, which humans can feel”
I haven’t looked too much into that paper, but yeah, it could be that at smaller scales you are just perceiving the friction.
But just from personal experience, I am pretty confident that at least in the 10μm-100μm range humans have high fidelity tactile perception, and are able to distinguish various patterns and not just friction.