It has everything to do with your post. You're implying that McDavid was two years younger last year than Eichel is this year, which is not true. They're the same age. McDavid last year was a year younger than Eichel is this year. Last year Eichel, at the same age, Eichel had marginally better stats and a better overall perforamnce in my book. Neither player had great tournaments this year. Eichel started out with the better performances while McDavid's been improving the past couple games. Neither player is on the best line of their team. Larkin-Fasching was USA's best line while Domi-Reinhart-Duclair is Canada's best line. Throw either of these guys in the tournament next year and they'd crush it, but we'll never know since they'll both be NHL regulars.
In his post-draft season he was scoring in the NHL. Not in his draft season, which is what this is for McDavid and Eichel. When someone says "17/18 year old seasons" they obviously mean draft year, pre-draft year.