Does “data availability” refer to the ERC20 balances for each account? If so, since they are stored on chain, they should have the same availability as the main-chain.
Would you say, then, that the advantages of this approach is only when some users update their balances multiple times within a side-chain block? Otherwise, you end up with as many SSTOREs as a regular token contract, plus the cost of the proof verification.
It seems to me like this scheme is to find a mean to “commit” some transactions that get batch executed within a single on-chain transaction.