Mark's observations seem valid to me. This was SP's pre CTC setup for ABS teritory. Signals would clear at the intermeiate blocks behind (going away) the train. Signals at the end of siding would behave differently, more based on approch circuits. So only a few intermediate blocks were clearing behind the train. Take siding lights would apply. Sidings had spring switches to save time leaving.
I saw this on the Saugus line riding the 'Mountain Outin' to Bakersfeild.
Other roads seem to prefer a directionl 'stick circuit' were only intermediates in one direction between siding would clear. The visible signal behind your train would stay red.