I've only really noticed it nearby Sacred Springs and Roofed Forests so far.

Cobwebs are supposed to generate in Roofed Forests, but not in the adjacent rivers.

We'll fix this in the next release - in the meantime, if you want, you can disable cobwebs from generating by setting "RTG Decoration: Cobwebs"=false in config/RTG/biomes/vanilla.cfg

Fixed in 41ff68c