The data-storage debate (OP_RETURN) is related directly with a monetary property debate (fungibility).
SPAM kills the fungibility of Bitcoin.
On Bitcoin, a chainanalysis tag is permanent spam on your UTXO. It cannot be removed. It pollutes the coin forever.
Grin mimblewimble blockchain does NOT allow this. Design prevents the metadata from being created in the first place. There are no addresses, no amounts on blockchain.. You cant embed CSAM or monkey jpeg on blockchain.
So OP_RETURN - problem is solved. The blockchain bloat is off the table and utility P2P protected.