That's a new one on me, but if the good folks at Snapper say it works I would believe them. I think it is a mower-specific trick though, because on my Toro if you lift the front wheels much it breaks the airflow enough to kick some cuttings outside of the frame.

They are talking about raising the front wheels to drop the deck in a slight nose down attitude. It seems to improve air flow for better mulching in some conditions.

I used to do this with my mowers...in other words the rear wheels were higher off the ground than the front.

'Rear wheels off the ground'...okay, I'll have to try that.