Yea. I didn't buy that case for S10+ for that feature by any means. I actually bought that case excpecting to replace it because I just wanted a case ASAP because I had just gotten my S10+. Walmart had that case in stock so I bought it.
Ended up keeping it the entire time I had the phone. It was so impressive what a difference it made in terms of the sound.
Don't get me wrong the sound is fine on the note 20 ultra as is, it's just that if I could get another case with this feature I'd be very happy. I recently bought a pair of galaxy buds plus since this is my first phone with no headphone jack. I find my self just putting one bud in if I'm killing time watching some YT real quick or something. So it's not a big deal.
This is the closest I can find but it's not quite the same I think.
specifically the picture showing what they do with the speaker part of the case https://images-na.ssl-images-amazon.com/images/I/71eGATlbUgL._AC_SL1300_.jpg
Edit: Damnit just noticed thats note 20 not note 20 ultra lol.