How is texture fetching handled for a ’master material’?

I have a master material driving most objects in a scene to achieve a specific look. It has a normal map, a diffuse, maybe even an ambient occlusion map to make everything look like, for example, yarn. Here is a screenshot from a Nintendo game that seems to be doing just that.

https://static1.gamespot.com/uploads/original/1544/15443861/2882878-screen+shot+2015-06-12+at+16.46.37.png

This master material has various instances that get fed additional textures for detail normals, albedos tthat are mixed a bit with the master ones etc. How is texture fetching handled for the master normals for example? Does the engine fetch the normal map per object / material instance, removing the benefit, or does it fetch it once per frame and apply it everywhere it’s used? What kind of pros and cons am I facing? I’m especially interested in mobile performance.

When you are speaking about fetching a texture, the cost is always per fragment(pixel).

Could you tell me more about how this works?