I did that years ago when I bought a Redmi Note 4 in Shenzhen and discovered that the Chinese ROM is very locked down. I created the Mi post, but I don't remember having to make a forum post (although it does ring a slight bell). AFAIK it was just sending a DM to support on the forum / app to explain why you needed to install the Global ROM rather than the Chinese ROM (and being a foreigner was accepted as a valid reason). About a day later they unlocked the phone bootloader remotely, and then I could install any version of the Global ROM I wanted.

I've bought all my subsequent ones (Note 5, Note 8, Note 11, Note 12Pro) in either HK or UK so they all came with the Global ROM, and I've not felt the need to unlock any of them, so not tried to process since. But it definitely used to be pretty easy.

I suspect the reason for the weird process is legal to ensure that phones in China don't get unlocked in order to circumvent content controls.