Sorry for the late response.
There are plans to try.Actually I've been working on that and I'm getting okayish results with good looking and performance. The main issue is the expression range being to big and complex. The mouth hole has to be able to move around the mouth surface an also be able to do that big creepy smile without breaking in the process.
Another problem are creases (or at least that's how glitch called them), those are lines that form around the mouth caused by the topology. In my case that happens when I use simple geometry with not much loops to make rigging easy, something similar to the image you posted, where the mouth edges are directly conected to the muzzle eges with no loops in the middle and using a subdivion modifier to allow the shrinkwrap to work. Glitch solved that in post production rendering the same escene two times, one with mouth and other with no mouth so they can mask those creases. I guess this could be solved with a very high subdivision level but I'm still trying more optimized solutions.
About why I choosed using booleans. I didn't know how to make the original type but also booleans are very flexible in this case. I can give the mouths any shape I want in any part of the surface without having to deal with weightpaint, only with some shading issues that are solved with the data transfer. Booleans still have some glitches at times like flickering, but that can be solved with any slight transformation. It's a bit tedious if you do animation but I guess it's better than masking every single frame in post production.
This is where I got the information about how Glitch dealt with the creases:
Viewing post in Mouth
Thanks for the reply!! Anyway, I myself forgot to check, so I also apologize for the late response :>
Okay! I tried 2-3 times, but yeah, the face turns out crooked (maybe because of my crooked mesh), and the mouth overall honestly looks kind of weird. I tried to create the mesh based on the face mesh from Lukasz’s model, since it worked pretty well for him, but it didn’t really work out for me. And yeah, I agree, booleans are still easier than that type.
I also plan to work on making a custom rig, since Rigify lags a lot when I have two or more of them. And my laptop isn’t really that weak (i7-13620, 4070).
I was really surprised by your Twitter post. Good luck working on that! I’ll be looking forward to updates)