What's this all about?

I was in the process of replacing some rotted wood and clearing up some crumbling mortar from this behind my wall in downstairs toilet.

I noticed this pipe and wondered if it was asbestos. I felt it and wasn't sure. Felt around the pipe and the back of it is completely smooth - only the front has the white finish (I imagine that a previous homeowner painted it before it was boxed in)

I'm now sure the pipe is plastic.

Do you all agree? And what could this material be on the front of the pipe? It feels too coarse to be only paint

Thanks very much in advance