> North of the SMART station the timing is different because
the approach of trains (SB) and departure of trains (NB) are
different.

To clarify the term "timing" a little: the crossing protection must activate around 20 seconds before a train reaches a crossing. This is a CFR/FRA thing nowadays, although it seems to have originated in SoCal when the PE started installing wig-wags in the 1920s.

Two or more tracks may be set up to activate one set of crossing devices. How train arrivals and departures on these tracks affects the duration the crossing devices are active is an issue separate from "timing".

> There's tons of gridlock generated in the process.

True, particularly when there is more than one track involved and more than one train approaching the crossing.