Turns out my dogs do know sit.
About two years ago, I wrote a post called, “My Dogs Don’t Know Sit!”. I described how my dogs couldn’t hold a sit stay when I stood still right in front of them. I analyzed the problem, and my conclusion was that part of the cue for them to stay was actually my walking away from them. This was probably because I added distance too soon when originally training the stay. I ended up with the perverse situation that my dogs would hold their stays if I walked around, jogged, dropped treats, or left the room, but not if I stood still. All three of them responded this way, so it was clear that I was the problem.