Proper shirt for wear with a Sheriffmuir

[Tobus]

You can wear a sheriffmuir as formally or casually as you like. Casually open with an open-neck even a Jacobean-type shirt or formally but if closed at the neck then best to wear a collarless shirt and jabot. If worn open then any shirt really with a bow tie or regular tie. So you have loads of choices and it’s up to you to decide on the look you want.

I will admit right off the bat that the formal end of Highland attire is not my bailiwick, but why would the sheriffmuir lend itself to being worn casually? It seems to be built with components that are typical of more formal jackets (tashes, square metal buttons, etc.). If I saw someone wearing one with a Jacobite shirt, I must admit I would think it looks very strange. Is this something you typically see in your area of Scotland?