...that he needed us to sign the paper listing him as the buyer's agent "only for this home" (his words), and that if we bought any other home, we could use any agent we wanted.

Then when I texted the broker to complain about the ambush tactics, she apologized and reiterated that we were "not tied to him [the agent] on any other properties."

Perhaps I misinterpreted, but it certainly seemed clear at the time that they weren't simply showing us paperwork as required by law, but we're trying to get us on the hook for a buyer's agent commission.