Interesting. If revs go up for the same speed when switching from Comfort to Sport, you must be dropping a gear. I wonder if Sport drops 6th gear (or whatever the tallest gear is in the autos)?
In the stick, I never go into 5th, and skip from 4th to 6th. Really, 3rd is tall enough to get to cruising speed, but there's no real need generally to top it out. I'll drop for 6th to 4th to pass or if I need a pop of power.