As has been variously stated here, 'Balderdash, bunkham, nonsense and piffle.'
This is just another myth perpetrated by the kilt police, kilt hire stores, eejits etc.
There are very, very few hard and fast rules about kilting. And those tend to be things like 'A mini-skirt is not a Kilt' and 'Don't wear a prince Charlie coatee with a hawaii shirt.'
Basically, common sense.
Some people just believe everything they hear and never look further into it before passing on their 'Knowledge.'