I disagree with the kid who is disagreeing. Like said above, you can move weight over the tips easier because they're shorter and butter more.
Imagine standing on like a 210cm ski, center mounted. Unless you are really tall, you're gonna have to try pretty hard to get any weight over the tips. Even if you lean as far forward as you can, I can't see the ski bending too much. Even on the downside of a roller, you'd have to lean very far into it to keep the ski flexed.
Take the opposite, standing on like 120cm skis, center mount. You could easily bend them, probably without bending you body too much. You could probably fall over from tip standing, or flex them enough to snap them in half.
I know those are extremes in length, but I'd assume those "rules" would still hold true at other normal lengths.