it's the same thing.

to use precise category theory language, sequences of blocks are arrows. utxo sets are objects. (arrows are transformations between objects and compose nicely)

we only care about arrows to get objects.

we only care about chains of blocks, to get the utxo sets that we want.

you could also think of the mempool as a giant blob of potential arrow (chain of block) components. since blocks are made of transactions.

I'm playing around with the math of this ;)