Yes, could be bedding.
Could also be impacted anal glands ...
Generally, if you feed raw, and get enough calcium, the dog struggles to poop ... and never gets impacted glands.
However, if you feed kibble, and your dog has big, loose turds, and never struggles at all (struggling helps express the nasty $#!^ out of the glands), they can become impacted.
Just a thought ...
Jack