... that's always been MY understanding too.
Perthshire ... referred to locally as 'The Big County'.
Um ... not directly, no.It actually borders Angus ... the Aberdeenshire boundary being reached at the approximate point where the dual carriageway skirts Laurencekirk on the one side - and St Cyrus on the other.
However, I'm familiar with the B-road you mention - via the small town of Coupar Angus - as it's a route my son frequently uses in order to bypass Dundee. Mileage wise, it's shorter ... but - with its many twists and turns - takes much longer to navigate.