I think it's great that your man steps out in a style he like to wear and feels comfortable in. I'm all for that.

However, for Scottish and Irish people, a kilt has a particular design and as far as I know, is always a tartan plaid.

A kilt (Scottish Gaelic: fèileadh [ˈfeːləɣ]) is a garment resembling a wrap-around knee-length skirt, made of twill-woven worsted wool with heavy pleats at the sides and back and traditionally a tartan pattern.

As a Scot I(but half-Irish) I would never see a skirt as a kilt.

Still fashions can change as can definitions.

I need to go back to your clan map. There's definitely a clan Rattray.