Here are two theories to investigate:
Viewing 3-22-18_01.XDL I see a restart at approximately 4:40.
At 4:40:716 I see knock counts increasing and knock retard of approximately 1.8 deg.
At 4:43:112 all traces of spark knock appear to be gone, and spark timing is significantly retarded.
GM released calibrations for 92 - 95 vehicles intended to reduce cold startup spark knock. You can read a copy of one of the service bulletins
here. Installing the cold knock fix calibration was one step in a matrix which included potentially changing oil filter type and replacing main bearing inserts. BJYL is one of the calibrations which was replaced. As I remember, shutting the engine down when warm would allow oil to drain out of the journals. The spark advance delivered during restart was enough to hammer at the bearings for a short time until oil pressure supported the crank. Over time this would cause excess clearance to develop in the mains. I wonder if it is possible that this truck's engine may be experiencing the same problem, and the knock that's showing at startup is the result.
But this doesn't answer the question about why spark is retarded when no knock is occurring. I would have to look at the code, but I wonder if the pcm will store a value akin to "block learn" for spark if it detects knock during startup. I have never heard of this happening but the theory could explain what's happening. I did scan for additional restarts in the 3-22-18_01.xdl file but I didn't see any. Possibly you will have additional log files to compare?
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