Interesting that you mention both the channel and the carpet with a nap to it.
A bipod that I have been using (Talon) has feet similar to the early SEBs... I did notice that it does tend to run it its own groove after a point during a string. Given that the lip is fairly shallow, I wasn't aware that anyone had issues with that.
As far as the carpet with a longer or deeper nap to it... a past team mate had a shag bath mat that he used... his gun tracked *great*. Far better than mine, and we had otherwise identical guns - same stock, same bag, same bipod. It wasn't until more recently that I made the connection... it wasn't so much that it dug a groove, in my observation, as that it just didn't allow the bipod to skitter along sideways like a hog on ice. The left leg planted rather than slid sideways, and that was that.
Given that the effect is very similar to what you get shooting with the feet directly in the turf/grass... I think it'd be stretching things a *lot* to say that the level of nap is something to be argued or regulated, in my opinion.