A little update on this. I went back to the lab and they apparently developed it at the development times for 800 iso, because that was what the table of their developer listed as the normal for Ilford Delta 3200. In fact, it didn't even list dev times for 3200, only 400, 800, and 1600.
This also checks out with this shot, because I vaguely remember messing up the math in my head, thinking that I went up and down a stop to cancel out, while I actually added 2 stops of exposure. Something I realized when cycling away. So ironically this is the only good shot precisely because it's 2 stops overexposed when measuring the church wall, which counters the 2 stops of underexposure from development. This shot would've been completely nuked if it had been developed as I intended.
Anyway, some learning for me and the lab. Next time I'll tell them the intended iso with b/w rolls.