In this longliner's humble opinion, @Than's proposed alternative isnt that far fetched particularly for novice skiers wanting to advance. The issue was kind of covered in THIS THREAD several years ago and has been foundational in my advancement.
A l5 offer who continues to pull long almost certainly will remain a 15 offer. Anyone who is half an athlete and has spent any time on a ski can eventually muscle their way thru 15 off. However, continuing that method disallows progress. Muscling thru by pulling long puts you in a horrible position at the ball, puts you out of position for the lean, which disallows enough speed to transition at the right time...and so the pattern continues stuck eternally at 15 off getting all six buoys with the wrong form. For many, taking a step back and missing some buoys to create the right form might not be a bad idea!
Most of you who post on this site are so good that this 15 off transition struggle is one that you've forgotten because you crossed it when you were like six years old!!! :) But for us mere mortals who lurk, this is a really big deal. I personally, for both myself and my kids, have found that the timing of the transition might be one of the most important elements for advancement because of the downstream ramifications of doing it wrongly.