Does his actual play match up with his numbers, is he getting some lucky bounces, is his skating still an issue, is he really contributing or feeding off McDavid, etc?
Yes and no. Players like Hall and Eberle have ten thousand times the talent, but never clicked with McDavid because they refused to simplify their games. Rattie, RNH and formerly Maroon however understand the basic rules of playing with a force like 97: Get him the puck and get to open ice.
Rattie struggles with making plays at high speed, but his work on the boards and in front of the net has been fantastic. Again, he knows to keep it simple- get possession, pass to McDavid, get open. Even if Rattie doesn't score on the initial shot, McDavid is still able to turn rebounds into highlight reel goals.
I am highly skeptical that his current scoring pace continues, but if Rattie can be a 30-40 point winger for $1M for less, that's a big help cap-wise. RNH looks like he can be a 30-30-60 LW on that line long-term, which is also a major development.