You are right about the speed but what could have helped him develop that:
If he would have been able to develop more force, he would have put it up, since the total force generated by a muscle depends on the numbers of active fibers and activity level in each fiber...what causes activation of the fibers is lifting a weight (lifting weights stimulates the motor units which in effect stimulate the muscle fibers, etc) take lifting a book for example-very little active fibers (compared to): lifting a heavy weight-here is a demand for activation of more fibers, partial reps would have helped him in this area, IMHO.
What I meant is that at the point near lock out his motor units would have become accustomed to the lifting of heavy weights, and It would have been no problem: an example of this increase motor unit activation is: say you want to do your max on the bench--try this do 1/2 rep with 20 lbs (or more) heavier than your max, rest a minute or so now go for your max and you will be surprised how light it is!
This is because by lifting heavier weight you cause your muscles to recruit more fibers than what they usually do or are accustomed to do. Heavier weight = More motor units active. Another example: shrugs: take two dumbbells that you can 1/2 rep (and do 1-4 reps), now go and rep your regular weights used for shrugging it will be almost as light as a feather! (well not that light but really light)!
I was never a fan of partial reps either, sometimes I wanted to tell the people I saw doing them that they should be going through full ROM, but had I said that I would have told them something I was not absolutley sure of. I hope this all makes sense. Another thing I found out from Physiology is that a contracted muscle is in its most vulnerable position when it is streched (or in full range of motion) that is why sometimes pec tears occur from heavy bench pressing or using range of motion on heavy DB flyes (the more you strech, more dangerous-that is why it is not wise to go down all the way or too heavy.)
Don't get me wrong, I still do lifts which involve ROM but also have included partials