1) How many unsolicited queries have you received, in whatever time period you like: month, quarter, year, forever?
2) How many turned into published books?
None will provide that data, but I strongly suspect that the answer to #2 is "zero."
They'll happily quote you BS quantities, like "a bunch" or "a handful."
So as this article says, they spend their time chasing celebrities, online influencers, and friends of friends. And not making a whole lot of money anyway.