MTP Do not work on official version , with TWRP-3.2.3-0810-XIAOMI6X-CN-wzsx150-fastboot everything is working fine. Tested on A2 converted to 6X.
that version of TWRP does work flawlessly on 9.5.15.0, it can decrypt data straight out of the box!
but sadly it works flawlessly only on that exact miui rom version.
I've tried on:
9.5.7.0 unable to decrypt data
9.5.11.0 unable to decrypt data
now sadly I'm on 10.0.2.0 it's unable to decrypt data, and I'm on anti 4.
I need TWRP for wiping cache + dalvik, which can't be done by this official version of TWRP nor the TWRP you've mentioned (I always need to re-format the data partition every time I boot to TWRP).
but that unofficial version of TWRP does point out something; even on stock miui, data can be unencrypted!