The reason for the factory reset when first installing TWRP is that it can't read the encrypted data partition so you need to format, not wipe, but format it. That is MORE than just factory resetting in that in erases everything from the partition. But once TWRP is installed, you can upgrade it by flashing the img file using the installed TWRP. That doesn't effect anything but the recovery partition itself.It seems I'm late to the game again, just saw this thread -
Twrp install without losing data Whats Not working: Support for metadata encryption (which causes mounting errors in log) MTP sometimes doesn't start until you disable and reenable in the Mount panel Instructions: From OEM stock firmware with...forum.xda-developers.com
This would be the same situation with X200XXU1BVI6? Just flash your new image through the TWRP app itself and I won't have to factory reset?