The problem is with the term "universal" and its association with the Government Sett. At one time in the 1880s, there was a move by Whitehall to force the Scottish regiments to wear the same tartan as a way to save money. The Black Watch tartan was going to be the "universal" tartan, but the move was successfully resisted by the regiments.

Over time, that "universal" designation has come to mean an "open" tartan, but its original intent referred to regimental tartans.

Stewart Hunting was worn by the Royal Scots Regiment, until its amalgamation with the KOSB to form the "Royal Scots Borderers", which is a battalion of the new Royal Regiment of Scotland -- and now, all battalions wear the Government Sett.

I would suspect that the Stewart Hunting's "universal" designation has something to do with its use by the Royal Scots, but I'll defer to Matt or Peter for more detailed information.

Regards,

Todd