pixelization

Hello
I downloaded a .sbsar corresponding to "Raw Slate"
It's a completely procedural material
My goal is to make a floor tile by adding the "floor tile" filter

The problem is that when I add the filter (material scale set to 2) this produces 4 squares but the slate material is then under sampled (pixelization)

This pixelization improves if I increase the output size for example in 4K but without corresponding to the sampling quality if I deactivate the "floor tile" filter layer

I do not understand why I have this pixelistaion when the base material is procedural

Can someone explain to me? and if possible tell me a solution?

Jean-Luc