Yes, I can definitely see that happening. And the main upside of an onsite developer in that situation is that a 'local'/onsite developer is much easier to identify when they are just sitting at their desk and much easier to encourage them to do otherwise. As much as people hate the "manager looking over my shoulder" feeling, it is very important in most workforces because the vast majority of remote workers (in my experience) will absolutely take advantage of the "remoteness" and use it to slack off. Sure, if you're a small or top tier company you might be able to solve this by making your hiring practices more strict, but the reality for most managers is that you must hire some of these less-than-ideal candidates and mentor/watch them, and being remote makes that harder.
I'm generally for the remote work model and this type of issue can mostly be solved by changing the way you interact with your team and do checkups, but regardless I find it strange that someone like yourself who is presumably very experienced in the remote work space would imply that there is no difference between a local slacker and a remote slacker.