Tried again with the latest version - all the updated firmware links for R5A wifi only were broken, so no downloads. Tried them in a browser, all 3 said files no longer existed. I pulled the old links (which still worked fine) from the previous release and manually downloaded the files.
The flasher worked like it normally does, did it's thing, and this time @ reboot it again said it was upgrading something, so I was excited that maybe it had finally worked. Once it was done, though, I was still on the same firmware as before. It looks like all it upgraded was switching me back to the correct region or something, maybe, now that the wifi-only version is available? The OTA update to R5A now shows up as available again, and the 'unlimited" apps came back. Other than that, everything else is the same.
So I don't know what's going on - I don't think there's anything wrong with the flasher, I don't think I'm doing anything wrong, but for some reason it just doesn't work for my tablet. It's clearly talking to it, doing something, making some changes, but those just don't include updating the firmware.
I'd love to hear any suggestions at this point?