Factory reset in Pie causes that issue. You can get the oem unlock option back when you downgrade to oreo. It will be retained after upgrading to Pie but do not factory reset otherwise you will experience the same issue.
It sucks indeed. This is the reason I decided to stay away from Pie for now. (unless someone figures out how to neutralize this FRP re-lock trigger).
In my case (CLT-L29 C432 - never modified, re-branded etc). funky method via HiSuite has always worked like a charm both with beta and official .163 but:
1)funky says they do not support this method anymore - so you do it t your own risk.
2) your system must be unmodified.
3) again you gotta pay for credit.
You can use FunkyHuawei to downgrade, but obviously, you will have to pay for it.
Actually, more devices are supported with the newer versions
---------- Post added at 08:08 PM ---------- Previous post was at 07:58 PM ----------
So I just tried with several versions of Hisuite (126.96.36.1991, 188.8.131.520/303_OVE) and nothing appears in update section.
Yes, the bootloader (xloader) will be updated, there's no way around it. Yes, downgrading works, but you will have to factory reset after downgrading.