Basically, Core says open up the OP RETURN field for other use cases than money, so they don’t misuse utxos like they do now.

Knots says, start filtering out anything that resembles anything other than transactions (spam) at the node level.

Two side notes: What defines “spam” is subjective, hence the discussions. And also OP_RETURN can still be dropped on your node so it doesn’t bloat your ssd.