I think there should be a new rule men fregt nisht kein kasha oif ah minhag, similar to a kasha oif ah maiseh. Minhagim rarely make sense we do it becuase our parents did it.
So why do those who dont eat gebrokts eat it the ladt day?
Because thats the minhag.
(Incidently, some only eat gebrokts the last day when the following year is a leap year)
Sam2 As far as I’m aware, the standard minhag among non-gebrokts eaters (present company included) is not to use charoses for korech.
As for viewing those who eat gebrokts as “less frum” Please switch every mention of black-hats in this thread http://www.theyeshivaworld.com/coffeeroom/topic/black-hat-2 to “not eating gebrokts” and the EXACT same conversation can be had regarding Gebrokts vs non-gebrokts (which is viewed as a chasidish lmisnaged divide)