It wasn't always obvious which trains used the Rose Street Curve. In the
early 80s I caught the sleeper to Inverness from Edinburgh and that
terminated by reversing into the North side of the station. A lot of mail
and parcels were carried then through to the far North and Kyle lines and
it was easier to transfer these on the North side of the station.

There was a 0655 from Perth as well due 0940 which did the same for the
later morning Kyle/Wick service. The Perth service carried vehicles that
had been on the West Coast Postal so again the cross platform connection was
useful.

AFAIK there was a plan hatched by BR when DMUs started operating to do away
with the Northern part of the station and reverse all trains into the
Southern platforms like they do at Killarney. With the increased frequency
of trains on the Southern end of the far North line I suppose that is no
longer an option.