In your opinion, would all other general work need to have an event specific duration as well? If this is so for Boxing, what would this mean for the 100m?
Remember also that Wells did huge push-up and sit up rep numbers of significant duration.
We also used to do depletion push-ups (3 sets to failure with 90sec between sets). The assumption here was that the muscles involved would lend indirect endurance to the rest of the musculature via the cross-over effect without risk to the muscles directly involved in the sprint action itself.
It might seem ironic but we found that BP numbers went up more rapidly and very likely other lifts were favorably affected as well. when this was introduced.
This was because of the variability of the challenge to the F/T curve IMO.