The first stats I posted in that post were the combined 2017-2018 and 2018-2019 statistics, because that is the time period you specified when posting your Domi/Stamkos stats. Domi was behind the other players.
The 2nd group of stats I posted were the 3-year sample, in response to this post by you, discussing 3 year stats:
Domi was once again behind the other players.
Raw points over an arbitrary threshold is a pretty misleading way of comparing difficulty of scoring, especially considering you're comparing the furthest apart years, including half of a year that isn't even relevant because it came after the signing.
Even if we are to assume that league scoring rates are factored into contracts (haven't seen much evidence of this from anybody, not just Dubas), the extent that league scoring rates actually changed is grossly exaggerated, and it's not a direct correlation with difficulty of scoring. Only part of the actual change is because of external factors like equipment/OT. We're also in a period of high talent, after a dry spell from weaker drafts and significant injuries to high-end players. It wasn't just conversion caused by equipment changes; shots and chance generation also increased because of the influx of high-end talent, leading to part of the scoring increase.
But.. for the sake of the argument, let's assume that the entire change in league scoring rates is caused by external factors, and let's assume that GM/agents adjust for league scoring rates for contracts, and adjust McDavid's scoring to the league scoring rate for Matthews' sample:
ES Points/60
McDavid: 3.05
Matthews: 2.72
ES Primary points/60
Matthews: 2.36
McDavid: 2.33
ES Goals/60
Matthews: 1.59
McDavid: 1.07
PP Points/60
McDavid: 6.67
Matthews: 6.47
PP Primary points/60
Matthews: 5.06
McDavid: 3.74
PP Goals/60
Matthews: 2.95
McDavid: 0.97
It still wouldn't change all that much. McDavid the better point producer. Matthews the better primary point and goal producer, with a good case to be paid a similar amount.
We should also remember that McDavid is a great value contract historically, due to the 750k discount McDavid gave on the negotiated amount, so even if you wanted to argue that Matthews' contract is worse than McDavid's, that doesn't make Matthews' contract bad.