It lets you build something like lighting (where two people can own separate amounts in a single UTXO) except non-interactively and without needing some “punishment system.”

Thats literally it, and it can do this at scale too, so you can do it with 20, 50 or even more people, because you just add more “sub transactions” that can validity spend it into a tree. Same as you do with signatures now, it allows you to add amounts and specific destinations.

In other words, we could open millions of lightning channels in a single block if we had something like UTXO, and they could even be “private,” as they wouldn’t have any apparent location on chain if you didn’t share it specifically.