Sure, that doesn't actually say best screen ever tested, it says "most innovative and high-performance display that we have ever tested". Best means most accurate, most innovative and high-performance could mean anything, which is impossible to determine without the context.
If they did mean to say it's the best, then that could be because the Note 7 came out a month prior to the iPhone 7, so the Note 7 could have been the best display around, for a month.
According to Anandtech's results, that would be true so long as we were willing to ignore the iPhone SE's existence, which most of us probably are. This also leads to another mistake of theirs, if the S7 Edge was the previous winner at DisplayMate, they ignored the 5X, which is not as easy as ignoring the SE.
The only other way they could mean that it was the best, would be for them to not know what they're talking about. I think we give them the benefit of the doubt that they just hadn't tested the unreleased iPhone yet, but given the S7 mistake, we don't have to give them that benefit, we just can.
Why is it that whenever people say "blah blah blah, period" they're almost always wrong?