Yeah but finding the other ones like you is incredibly difficult. People in their 30's and 40's with zero friends looking to make new ones are basically non existent where I live.
Interests connect and these guys hardly ever meet or met someone that intersects as much, so they clear their schedules (as do I) to foster a friendship.
I met most of my friends, business partners and clients this way. Overlapping interests and chance encounters.
I meet plenty people on internet in subreddits with the same interests and sometimes we meet up and then it clicks or it doesn’t.
Why would they need to have “zero friends”. It is not like people have a max number of friends they can have.
One person was really blunt with me: "you're a pretty cool guy, but I don't have time/space in my life for new people". Other people are less blunt but the same principle applies.
edit: But maybe that's my British instincts wrongly diagnosing a statement that I have no real context to judge better.
I just feel that if it were possible to track every time that sentence is said it would probably be significantly more often used as a polite excuse rather than as a truthful statement. (And even then, that's my gut feeling / assumption, I may even be wrong about which use is more common).