PERSONALLY I really don't like it and would never have any of my athletes use it for one main reason: they need to be good at the front squat and squat cleans. To me, this drill (scrape the rack front squat) teaches bad motor habits of pushing forward and driving with your toes when standing up from a squat which is a no-no when doing regular front squats and olympic lifts.
Personally it would also kill my elbows and if you take a proper front rack position it would choke you.
But it you like the effect, do it. You can't argue with results.
I don't hate it as much as the first one and I can see it as having some value if one wants to practice pull-ups daily without overstressing the body. But from experience if you stop doing regular pull-ups, any gains you might make from this one would not transfer to regular pull-ups. I learned that the hard way when I only did bench presses from pins for a long period and my capacity to perform a regular bench press diminished despite stronger muscles.
Removing the eccentric is a good way to get more volume and frequency in... but it helps strengthen the concentric, but not the eccentric function of a muscle since both contraction types have a different motor recruitment strategy.