I guess if he already booted to recovery using key combo such ROM patching is not working / occurring.
There may be a number of issues:
Enabling 'Keep system read only' prevents such patching. (I guess there may be additional issues w/ modern shared-blocks filesystem too.)
ROM may also have harder verified-image-protection to defeat. Some who found twrp fails to patch simply flashed Magisk which also prevents overwriting recovery. (Likely won't help here.)
I suspect he may also simply have booted using 'fastboot boot twrp.img'. PW