I had tested with stock firmware on the Redmi AX6S (mt7622 and similar to RT3200) with an iPhone 13 Pro before I flashed OpenWrt,.
The problem with upload speeds only happens with OpenWrt/mt76 driver. With stock firmware (AX6S stock firmware had support to 80Mhz) there was no problem with 802.11ax and upload speeds.
I had posted the results of this test in that topic here.