Wait, it's not wrong at all. It says that you can go for max if you need to take a boss down in as few hits as possible, but that the more reasonable approach is to keep your options open and you potential loss at a minimum by going for 60%. I wrote it up up there, it doesn't box you in strategy wise as much as "The correct strategy when boss-fighting with a Crusader and Momentum is to kill as much as you can without leveling, hit the boss until you run out of health and mana, kill more popcorn to level (and as much as you can until you're about to level again, supposing you have enough to level twice), and repeat."
As choongmyoung said crusader is the immunity (and also altar juggling and consequentially resistance stacking) king. If you're an Orc you can try to cheeze momentum, but most other guys don't really have to worry about it. I might have been more harsh towards "go for fewer hits" approach because the page used to say pretty much "THE ONLY WAY TO PLAY CRUSADER IS TO BE AN ORC HUR-DUR AND GO FOR HUGE MOMENTUM". Then I change it to be about the actual Crusader rather than one particular and not very sensible Crusader (doesn't make a lick of sense in Gaantelet). Then random newbies can disbelieve and argue and protest... and in several years I see them writing about how they discovered that the crusader is more about his other abilities than momentum and essentially what was written on the wiki all along. This actually happened.
So it's not really bad advice at all. Point of it is - make sure you're at 60% if you want Momentum to matter. (EDIT: Which is what, if you pay attention, the ability icon itself is telling you. As does the gold Crusader challenge.) If you would want to go beyond that is determined by circumstance. But if you are Crusader and you worry about getting hits in on something so much that gobbling up all the popcorn is a better deal then you are playing a very specific and not all that optimal crusader.
Also if you're going for "get a bunch of big hits in on the boss" you're likely going for dodge potions. Those are actually difficult to trigger or operate properly if you've eaten all your popcorn.