Those two decoratives only appear to spawn underneath biter nests, and are colour matched to them. I like all my shrubs, so I don't want to turn on the "remove all decoratives" filter—it would be nice if the biter-exclusive decoratives were included under the Biter Goo filter.

Certainly, I simply tested it on a single playthrough in a few select areas and was not sure what else would only appear in biter nests. In my limited tests I didn't see any where I went "Yup that's biter stuff". I will look into it and add them.

I don't really see any difference with or without those, neither in vanilla nor in my heavily modded game. They do exist according to the game at the place I am looking at, but it's not visually different to me after removing them. Regardless they will be added with the next update.