Well, to start with I'd actually want to see the memo to see the exact wording, because there is a biiiig difference between a 50/50 call and interference that looks outrageous. I'm skeptical the memo left that kind of room for error, and those two statements are at odds with each other.
But then I'd look at, as an example, the McDavid interference and I'd say that isn't a 50/50 call. It's clear interference. McDavid skated right through the blue, made contact with the goaltender, and pulled him out of position. Since a defender didn't put McDavid in that position(ie push him in), that's an obvious call. If a defenseman somehow contributed to it, then I think it could be 50/50, depending on how much effort McDavid makes to avoid contact, how much force it looks like the defenseman applies, etc... That just doesn't apply here.