It's effortless to get NIP-05 from Iris. Still, enforcing NIP-05 verification on my relay has cut down on a lot of spam.
Discussion
And with others too, Current for ex.
But people will wear them like badges, will switch between them from time to time:
bitcoinaz@Voltage
bitcoinaz@Swan...
bitcoinaz@CoolNameHere
From what I've observed though, the most egregious spam comes from random npubs with no profile data or NIP-05.