I believe this advice applies mostly to how to play position for the correct angles, not how to deal with the wide array of shots that arise during a game.
Bunting balls so softly they barely go into the pocket is risky. Balls can roll off, skid, etc.
Excessive force shrinks the pocket and can lead to a jerky delivery.
There is a nice, smooth, crips speed that lends itself well to accuracy of delivery while keeping the pockets playing comfortably large.
Clearly there are times you'll need to deviate this. But when playing position it's advisable to obtain an angle where you can use this speed of stroke. And when you are hitting your positional spots right and keep leaving yourself the appropriate angles, you may indeed be hitting most shots at the same speed. I think we'd all agree that when a pro is playing well that once they get in line they shouldn't have many shots they dribble or blast. Exceptions would be if they get out of line or in a very unusual spot.
I have to tell you that I am guilty of hitting balls very softly so they barely go in in some instances rather than having the cue ball travel 2 or 3 rails to get to the same spot. If the equipment is good there is no roll off.
By hitting the balls the same speed, he might mean all shots should be hit firmly or with intention. I have a theory that skidding is caused by slowing your stroke through the shot rather than dirty balls and such just as most miscues are caused not by lack of chalk on the tip but by coming out of the shot or getting up ever so slightly out of the shot. Just my opinion.