This is all there is to it. Hes not leaving the golden goose but hes not going to stay if said goose is getting the hell out of dodge.
Though he could demand a trade out, it is very hard to figure out $14 mill or whatever the number is of cap space for like 7-8 more years between 2 teams for a trade. Plus, with NTC would be hard to even up the players going the other way.
So, would not be easy to get out or to a place he truly wants should he sign for max term and then McDavid doesn't stick around.
Way easier to facilitate a trade this off-season with just 1 season left.
Or, something crazy and he extends 1 year to match Connor so that he's not left there.