I don't see why the one should rule out the other. Print-on-demand doesn't have to entail version-on-demand, which sounds very messy if there isn't something to refer to.
Let's say they called your version, "Version 1". Mine has Chapter J, so that could be called "Version 2". If the difference were documented, someone with Version 1 could see that Version 2 now includes Chapter J, and whatever other changes are there. Version 3 could be the one with the HtH rules folded into Chapter A. Again, if this was clearly stated, someone with Version 1 might see a clear reason to update to 3, whereas someone with Version 2 might feel that they already know where to find the HtH rules if they need them, and wait to see what's in Version 4...etc.
Throwing in changes ad hoc without versioning sounds like a recipe for chaos.