Now I was reading that link to eBay and saw this;
Blade Blocker is not intended to be used as a mulching plate or in the place of the discharge shield. Its purpose is to temporarily block the discharge opening in order to prevent large volumes of grass clippings from being discharged onto areas where they are not desired.
Is that for liability reasons the company puts that on there? Or, is it truly not meant for say, leaf cleanup, and it would cause other issues? I take it you have had your for a while and mulched leaves before?