Thanks for pointing out it’s worth underlining this in the writeup. Will edit OP.
I do also think this is what drives most of the IBD speedup there. And it is directly related to their architecture, doing it for Bitcoin Core wouldn’t bring much benefit since you still have to update the UTxO set (see also this #bitcoin-core-dev discussion discussion about this).
Yes although in the context of this specific benchmark it’s more about being able to skip a whole class of checks than parallelizing them, i think.
Even if they do, we can expect there still being an edge in using a UTxO set (as long as it doesn’t get enormous) as you check inputs against a much smaller index.
This isn’t so much block storage which makes a difference but how their content is indexed. In this case it would be clearer to make a distinction between a historical transactions index vs an unspent outputs index.