This is a small bug, but I don’t have access to post there.
I’ve read the announcement about how the textures of the surface types will still be available for plastic parts for aesthetic.
However, the option was not there when I created a new plastic part. I only saw the option to change the surface type from the classic baseplate. So, the only way to edit the surface types on a plastic part is to clone the baseplate.
Thankfully, I found a plugin to easily edit them, but for people without that plugin you would need to clone the baseplate and their clones.