In February, Xiaomi stated that the Redmi Note 9 Pro would receive MIUI 12.5 in late Q2 2021, a period that we are now in. However, the device has just received a new upgrade, and it only contains Android 11. For some reason, Xiaomi has decided against bringing MIUI 12.5 to the Redmi Note 9 Pro yet, for some reason.
https://www.notebookcheck.net/Xiaomi-upgrades-the-Redmi-Note-9-Pro-to-Android-11-but-holds-back-on-MIUI-12-5-for-now.545961.0.html