Incorrect. OP_RETURN is not usable for ordinals because the outputs are unspendable. So you cant transfer that rare numbered sat because it will error out when you try. What this allows is inscription of data other than transactional data, without needing the script interpreter (it basically errors out on the first byte of the script, which is OP_RETURN itself)

The important thing is that you can, after hashing, completely discard the UTXO because its not spendable. And thus it doesn't pollute Bitcoin Core's (and forks like knots and libre) utxo db. From memory I do think that libbitcoin indexes them but even if, would be easy to prune them if you don't need them.

The current limit was imposed because it was deemed enough for counterparty back in the day. The reason to expand it (or drop the limit) is because Citrea threatens to circumvent it and fill up the utxo db with fake keys.