I think this should violate user privacy in some way if they've silently forced this update upon people without consent! not surprised to see this happening, did warn people to avoid Grey market traders for a long time now... Thats why the names of Grey traders are censored on our forum so we can't and wont advise where to buy the devices.
1.Just not lock bootloader and You dont get bootloop. If You want lock bootloader You must flash to stock rom example for Chinese version Phone You must flash to Miui China and lock bootloader.
2. If You have lock bootloader dont try flash via Updater from China Miui to Global or from Global to China, because You will have bootloop. Thats all.