MIUI 12.5 just started testing, so it's going to take a long time to release it as stable on global, since the current testing is going on for China. China stable version is expected to release in April, and probably after that Global will start testing and that's going to take another while.
And also Xiaomi released Android 11 for Mi 10 recently but I think it hasn't arrived for global yet, I checked on the official Downloads page of MIUI and the downloadable ROM's are still Android 10