To clear my understanding of your first statement, you're saying that their "lightweight / low memory" claim is invalidated by components having one unnecessary level of nesting in DOM?
On a related note, I’m curious if anyone has a benchmark comparing performance and memory consumption when attaching a shadow root vs not.
The results are here: https://raw.githubusercontent.com/jjcm/shadowTests/master/re...
TL;DR - the withShadow element takes about twice as long to render as the withoutShadow element. Don't use them unnecessarily.