He's Paul McCartney…he can apparently call his album whatever he wants to. It's not a demand from his tour rider, it's a lyric from a Fats Waller song.
"I'm gonna sit right down and write myself a letter and make believe it came from you; I'm gonna write words oh so sweet. They're gonna knock me off of my feet. A lot of kisses on the bottom, I'll be glad I got 'em'"--Fats Waller, "I'm Gonna Sit Right Down and Write Myself a Letter"