So is this the result of LA blocking BNSF's planned port yard?

I am just guessing. This moves 40 and 20 foot box blocking from the expensive and crowded port to cheper Barstow. More efficient and faster. The port simply loads every BNSF bound container immediately onto a train to Barstow.

No need to store them at the port. Sort for destinations at Barstow with more room and designed for that. Store as needed on cheap desert land. Simplified process means less impact by surly delay loving port union goons. Opens more domestic capacity at BNSF LA basin ramps?

UP Santa Teresa westbound does a similar blocking for ports. Eastbound UP is mostly building trains in port area for destinations. ST may expand someday for similar eastbound.

BIG tries to lure future 40/20' to 53' containers sort warehouses to Barstow instead of increasinly expensive Inland Empire. Eliminates port to these new warehouse trucks. But adds new warehouse to local distribuition truck from Barstow into the basin. In theory it should be a net reduction in truck miles for greater LA. But maybe a wash. And more trucks over Cajon.

Truck traffic to existing sort warehouses in LA and Inland Empire should stay the same. As would truck traffic from these sorts to local distribution. No reason to send that out of the way by train to Barstow then trucked backed to the IE sort warehouses.

Maybe some port to Vegas trucks shorten to Barstow to Vegas?

Independent Mojave intermodal proposal does not look similar. Not helpful for sorting containers for the Sunset route. Just north markets and east via North Platte route. Which could still be Chicago and Northeast. But not yet a UP endorsed project?