I clicked this thinking it would be about some ATCO stinking up a tower...
I think you're confusing yourself, met briefs are in true "every thing the met man says is true" the irony of course being that it rarely is.
ATC will always give magnetic, although I'm sure some would have the ability to give true were it requested, like asking for "true bearing, true bearing".
Why would they want you doing extra mental gymnastics when they've just cleared you to land?