I'm HTC_001. I will give it a try a guess. Just one question before:Anyone with matching CIDs and MIDs:
MID supported: 0P6B10000
CIDs supported: HTC__001, HTC__002, HTC__016, HTC__032, HTC__102, HTC__203, HTC__304, HTC__405, HTC__A07, HTC__A48, HTC__E11, HTC__J15, HTC__K18, HTC__M27, HTC__Y13 and of course SuperCID: 11111111
No. It's not custom ROM. You don't need to erase partitons (wipe data).
It's a full RUU. Phone is completely erased during flashing like with any other RUU.exe or RUU.zip. Only data on external SD card are safe.
IMHO, RUU is much better than OTA. OTA basically is only the patches for current system. I prefer (with big Android updates) flash everything from scratch using RUU with full wipe.
It was told before that this RUU has the files exactly the same as within MaximusHD 12.0.0. Firmware in MaximusHD is 6.12.401.4. 6.12.401.12 is probably just a typo.I think that the system is indeed still .4, as far as I know, there were some problems with radio and firmware, so if llabtoofer says it is based on .12, it may indicate that it is based on RUU .12 which contains firmware .12 and system .4
anyway, I am downloading this too, will test it, in the worst case I will upgrade again to .12 base later...
No, it's no necessary to be S-ON or with locked bootloader. Just be sure you flash stock recovery before taking the OTA.