He must have a lot of spare time and really good patience to listen to 5000 or more songs for each one he chooses to do. Doing simple maths.......At an average of 3 minutes per song that is a lot of time to spend (approx 250 listening hours) or approx 6 weeks solid listening from 9 to 5. I am afraid I would have some advance screening process to weed out the weak songs and songwriters chaff before listening to any songs worth considering if it was me.
I on the other hand would have the opposite problem I would want to record 5000 plus songs..... I have heard some great unrecorded and written so many good ones myself....LOL

PS And they say that nobody allows songs to be pitched to them these days well this guy must go through a few pitches from songwriters....@ 60000 or more per album.