The reasoning is exactly right, the British MoD wants all Scottish units to wear kilts, because to the outside world: Scots wear kilts. What is intended is that this will be symbolic of the British Empire at it's height.

The UK Government gets credit way out of proportion for it's size because the Royal Navy kicked but at Trafalger, because the RAF stood against the Luftwaffe in the BoB and because the Scottish Regiments were the backbone of the greatest empire that this planet has ever seen.

If I were a Brit Diplomat and could say we kicked your *** and you Daddy's *** and your Granddaddy's ***, and we still can because we still have men in kilts, then the money spent would be very well worth it.

Nobody except us on this forum even knows what trews are.