Shulker mob switches broke in 1.16 because they don’t count towards the mob cap when they are in a minecart. Can you make shulkers in minecarts count towards the mob cap like they did in 1.15 please?

Why not just removing shulkers from the minecart? It's not that difficult, gnembon already made a design for that.
However, if this is implemented, why not just any mob in a minecart counts towards the mobcap, not specifically Shulkers?