Yeah, thanks. I recall a later video he did where he talks about how his thumb is constantly moving depending on what his fretting fingers are doing. I think he used his iPhone to show his thumb position for various chords.
Phew! Not the first time I’ve been saved by a legal technicality!
There is never a clear answer as has been mentioned before. We are all built differently. It is a matter of experimenting to see what works for you. There are some things that need to be avoided to avoid injury such as excessive wrist bend.
If you feel you have to bend your wrist too much then do not attempt to work through it. You will hurt yourself. Instead look at your guitar position and your elbow. It will take some time to figure out how to avoid this but your body will tell you if it feels wrong or right and with work it will become automatic.
Here’s a link to my experiences with Trigger Point Therapy to treat pain caused by poor technique. There are lots of other suggestions in that thread as well.