Alright, here's where I'm at. I went back to stock using the link provided by OP. Once in stock, I tried to do OTA update, but every time it failed with an error. I was able to pull the update.zip file from my watch, and tried sideloading it in TWRP. Here's where I was able to read the actual error. It read that the update.zip file is for catfish_ext and that my watch is catfish.
1) Why would system update download an OTA file that is not compatible with my watch?
2) I DO have catfish_ext (Ticwatch Pro 2020).
If anybody has any use for it, here is the OTA update file:
catfish_ext update.zip