I mean, if you want to see the GDC’s intent, the original rule for In The Zone was 48" cylinder, which was changed to 36" cylinder, which was changed again to the current rule tip-to-tip. You could read the reasoning here: Answered: SG14 Ambigious Wording - #2 by VEX_GDC
In short, yes to everyone above, it’s to make things easier to measure in inspection and on the field.