Caught on Camera: Amtrak's Two Indication Block Signals?

 Twice in the last year I have had the fortune to catch and video the strange situation of Amtrak intermediate signals transitioning directly from Stop and Proceed to Clear.  The first was at the 592 automatic on track #1 eastbound at Irishtown Road, part of the ~2006 Rule 562 CTC project, after the passage of the eastbound Train 42 Pennsylvanian.  The second instance was at the 133 automatic on track #4 westbound in Radnor, PA, an origional PRR signal dating from at least 1948, after the passage of a westbound SEPTA local. 

This effect is not universal so I don't think Amtrak has gone around systematically eliminating the Approach indication for "safety" reasons (although I wouldn't put it past them) so my best guess is that the 75ppm code generator at the next signal location down the line has failed resulting in the featured locations seeing a 0 code for an occupied block. Because train traffic hasn't been busy enough for one train to be running behind another, I suspect that in both cases the defects had simply not been noticed/reported.