Why?
That's typical. If you write the music, you get 50%, if you write all of the lyrics and vocal melodies you get 50%.
That's why on "Closest Roaddogz" for example, Johnny has 50%, Pac has 25%, Syke has 25%.
It's the same in my band. As a songwriter I also have full access to the PRS database, so I can type in the name of any songwriter and find their entire catalog, including unreleased material. It's pretty interesting, I discovered some unknown unheard songs from many of my favorite artists just by trawling through the database. You can find out all the writer splits on there too.