They don't remove it but they do reduce it.

I have an inbox, and I do not receive a lot of scam post. In fact, I don't think I received any since I lived at this address (~10 years ). We do get a few promotional leaflets every other week.

OTOH, I get hundred of spam emails every day.

The former is something which I can handle manually easily, the other is not.

If you are targetting a list of well-known authors I guess outsourcing the writing of a couple of hundred handwritten letters shouldn't be too hard. I'm sure they they can find a school class in Nigeria or Kenya who would gladly do it for a few dollars — or a struggling teacher willing to get creative with the homework assignments.

he doesn't need to process every invite. There is the murky middle ground, but it would be easy enough to pick out one a week say, from the list, as there are still tells (often related to details which deviate from generic) that allow quite reliable selection.

If nothing jumps out, it's not like he is losing out, it's just 10 minutes a week work to find that genuine invite.

I suspect it's more the human admin around the invite that is grating. It's not just AI invites that mess you about

I'm not doubting spam exists, but there is many using AI as an excuse to cut services they have other motives for avoiding