Oh, I created the flashable zip days ago. I was the one who caught the ota file this time [emoji6]. One of the ones I should say.Those instructions appear to be for the TWRP flashable, which as mentioned above and in the edited opening post, is pending:
With regards to the 'and then the zip from post #671 after you have booted to the system once', I'm not sure if using the OTA update on a device with TWRP would work, since stock OTA updates typically require the stock recovery to update the GPT, bootloader and other usually non-modifiable partitions. You may be able to edit the OTA file to ignore the stock recovery check, but again, it might be worth waiting for the updated OPJ28.111-22 TWRP flashable to be released. You could then flash the TWRP flashable and not have to worry about OTA updates, which should also leave your GPT and bootloader unmodified.