You need to be LOGGED to submit the unlock request...
And yes, the unlock request is tied to your MI ACCOUNT, you can request the unlock even if you don't have a Xiaomi device, you just need a Mi account.
It's simple, just wait 10-15 days and the Mi Account you used for the request will be aproved.
When it's aproved you need your device flashed with a Developer ROM. Then you need to login to your Mi Account on the phone and download the tool "Mi Unlock".