That "thermal zip" is doing much more, it patches fstab file so the mount options for userdata are changed for both system and TWRP. In other words, TWRP cannot work properly with userdata in format which MIUI is using. In order to solve this TWRP deverloper suggests to patch fstab.I have installed the latest miui eu using twrp (TWRP 3.3.0, cleared userdata to install it). It seemed to work ok (wiped data and flashed zip). But after the first boot on miui EU whenever i Try to reboot into TWRP (volume up) it stays stuck in the teamwin screen and never boots into recovery. Anyone has passed this? I haven't installed the additional thermal zip, could that be it?
The fact that TWRP has issues with MIUI encryption is indicated on the very first page of this thread.