How anyone makes it to this level and shows up for a check ride without, at a minimum, knowing the limitations and memory items is beyond me. That's pure amateur hour and inexcusable.

If you're not prepared, for whatever reason, call out sick if; but don't show up not knowing the basics. Of course, everyone can have a bad day. But those are the basics...it's a given those questions will be asked. If you study nothing else, learn the limitations and memory items. Getting a few questions wrong on other system stuff really isn't a big deal.