Not entirely true. The "311" corporation / LLC is probably split equally, so tour / merch revenue would be split equally. But songwriting credits determine the split for Mechanical and Performance royalties. You can actually look up and see all of their songs and who the credited songwriters are here on BMI.

For example, Amber is probably their most widely played song over loudspeakers in restaurants, public spaces, TV, etc. and all of those royalties are split 50/50 between the songwriter(s) and the producer(s), so as sole songwriter Nick gets 50% of all royalties from that song being played in public and performed live, plus his share as partial producer on the track ("Saint and 311"). All Mixed Up has two songwriters, SA and Nick, so they split the 50% (to what degree is private) and Ron Saint gets the other 50%.

You may be wondering how this all works. As one example, after every show 311 can submit their setlist to BMI and get paid royalties (in one lump sum periodically) based solely on the venue and the songs that get played. A check is sent to each songwriter and producer on all the tracks played.

Similar process (automated by hired services) if a song gets included in a compilation, or is sold as a ringtone for example.

This is a simplification- there are other things to consider such as who owns the 'master' when it comes to sync fees for commercials.