I'm not sure anymore is the correct word, because I noticed disparities after barely a month of TVE availability. (I matched TVE content with what was broadcast over cable, and rarely did they ever coincide.)
If what you say is correct, a simple layman's guess would be that the feed being sent is for the highest numbered alternate when available; only if there are no feeds on any of the alternates does the primary feed get delivered. (This seems contrary to other sports RSNs that have dedicated alternates available with TVE: NESN+, NBCSN Philly+, SECA (does that one have a TVE feed?) ...)
I have a couple different sites around SoCal I can use with various cable/satellite providers to try TVE authentication and grab some detailed logs if it will help. As I said, personally this doesn't really impact me, but I have family who would like to view these extra channels.