Straight weight at 80% definitely different than 50 straight and 30 band tension.
However, doing singles with straight weight at 70-80% you can generate significant speed and has greater carryover to your max bench. I doubt most who ever did speed work took the time and timed themselves at .7m/s to see if it was actually considered speed work. That time frame really doesn't mean anything in the real world. Fast is fast. Can you be fast with 70-80%? Yes, if you're strong and done using singles specifically for speed on the concentric portion where it counts.
It's also difficult to determine whether or not speed work was useful towards a max when doing heavy inclines db's, triceps and upper back work when that particular weight was heavy. More than likely, since using a full ROM with the heavy assistance work, it probably contributed more to a 10kg gain than the speed work did.
Take a look at CAT training. Read about Fred Hatfield and Josh Bryant concerning that training.
I'm not against speed work, but for raw lifters and especially those only having a few years under their belt, it's just not necessary or helpful towards building a total. If you read enough, you'll find "offseason" speed was done in the 15-30 set range.