I had to do a visa-run in Vietnam a couple weeks ago and my trip to the border was exactly like that. After the bus got to their nominal final stop, they’ve unloaded all passengers except me, then made a couple other stops (they took a computer monitor from one place to another??), then finally told me to wait and take another bus, which I didn’t have to pay for. (Both buses were of the micro-bus / marshrutka kind, of course.)