Ah so that's where the 's' came from. Seriously never knew as I always understood it as "I'm making my final approach" hence 'final' without the 's'. Every day's a school day
As for the(A)FISO RT, it shouldn't be confusing to hear plain English waffling. But I'd be expecting to hear "... land at your discretion" (which we all do anyway; FISO, Radio or full ATC).