Orginal spammers doesn't really care about the fee because the 0.1 or 1sat doesn't stop them from minting their useless tokens but I agree that lower the fees the more chance of spamming the blockchain.
With 1 sat/vByte, they need to pay at least 50 cents for an Ordinals mint (as it takes basically 2 transactions) and about 15-20 cents for Runes. You can do that once
compĺetely without profit expectation but not 1000x. For 0.1 the same basically would apply, it would still not be "free" in the sense you can create hundreds of mints for a few cents, because every mint would take a few cents. 0.001 is 100 times lower, this is basically the fee level on Litecoin.
So I think it makes a difference.
For spam protection, there is the datacarrier=0 which is much more effective. Also, there is the (OP_FALSE OP_IF) filter bugfix implemented in Bitcoin Knots.
Unfortunately this only targets some types of spam. There were several protocols published to evade such restrictions, simply encoding the token data in "normal-looking" public keys (basically what the first wave of coloured coins did in 2014 approximately). The probably most well known example is
Stampchain. Fortunately they didn't really get a following but that can change in the future.
And it seems the datacarrier option isn't used enough to deter Ordinals who have grown again a bit in the months.