So.. I continued to try tools, bupdater (both older and newer versions) and aflash2 (aka ASUSTeK ACPI BIOS FLASH UTILITY 3.12).
Until this later (even though giving a "perfectly working impression") bricked my computer badly.
I thankfully was able
to invoke amisetup(?) "flashing..." recovery menu and fixed it.
Later, I was left wondering whether such mode couldn't have
decreased security and tried to trigger it elsewise (no way I'd been risking the laptop again).
But I just found out ctrl+home combo in "uneventful times" just opens stock ez flash utility instead. Only then I took notice of the
Secure Mode marker so evidently stamped on there.
Of course I couldn't help myself but checking for the disassembly of ASUSEZFlash binary... And of course with my
limited nonexisting skill I couldn't find a lot.
So I tried to compare it with the one of previous bios versions.
When I saw Asus Setup Menu spec was mentioned to have been introduced only in the second release.
Hence I tried to downgrade to the first, cause who knows
(e.g. here, newer uefi supposedly hides secure boot options in at least some situations). And for once I was hoping winflash could be useful given that was just an official fw.
Unfortunately it entered a kind of loop, failing at 3% of verification phase, then restarting.. and I decided to kill it from task manager. With great surprise on my side, for the first time in my personal saga of NOR writing gone bad, having no system locking up royally to report of.
Instead of taking advantage of the situation to quickly reflash 212 though, I frenetically decided to reboot.
Now I'm sitting here, looking at my undead laptop, that contrarily to my last fuckup isn't seemingly even trying to access USB devices.
So I fear this may be a goodbye.