Hm iirc if you do not boot to TWRP instantly after flashing, MIUI will revert to stock recovery.I am trying to flash it on my CC9Pro Premium, but the xiaomi recovery is still there and TWRP is simply not flashed. Everything looks fine while flashing it via fastboot, but it simply doesn't apply. Any clues?
After flashing in fastboot, hold "volume up" button and enter "fastboot reboot", see if that helps.