Just a comment
"- The speed brakes were manually engaged about four seconds after touchdown. Thrust reversers were deployed about seven seconds after touchdown."
It seems to me that 4 seconds is a long time to get the spoilers up. Just me, as soon as I had the thrust levers at idle and was on the ground, I was pulling the spoilers up (707/727 and 737 with inop auto-speedbrake)
3 seconds after speedbrake deployment might be OK for the T/R's to be fully open.
Maybe he was pulling on the reversers first, and being unable to get them up due to no weight on the squat switches, then remembering to pull the speedbrake handle?