lets look at it a different way. a truck means everything from a pickup truck to a semi. They have a 'ugly stepchild' of a suv.

A hat includes flat hats and ball caps and cowboy hats. They all cover the head, their ugly stepchildren include visors.

a sword includes everything from Kukris to flamberges and claymores. I wouldn't call the daggers their stepchildren, more brethren their.

boats include everything from life rafts to navel carriers. I guess subs would be their ugly stepchildren.

So why should kilt be so narrow a view? Beyond tartan, where it sits, pockets or not (come on, I bet if they figured out how to put in hidden pockets 200 years ago, they would have done it. Or even the removable cargo pockets.)

or in other words, did a hat stop being a hat once they put these clapping hads atop them, or when the cup holder and straw tubes were added to make the beer drinking hat? Why then apply that same set of rules to the Kilt?