I really don't understand the problem there. You also run into the risk of him putting up 50 or 60+ goal seasons over the next few years... and now what. 3 years at 19M or 20M per? Or whatever the max will be by then. Maybe he decides he wants to go play for a US team in 3 years and walks for free with his NMC. There are lot of ways it can go wrong with a 3 year deal.
Even in his low years, he's a premier top 5 center in the league, if not top 3. I really don't share the sentiment that his health is a concern at all. I'd rather overpay now over long-term with a chance he'll outplay his contract over paying top end dollar every 3 or so years.
It really just sucks in my opinion.
Last year, it was clear Matthews shooting wasn't right. He ended the season with
12.2% shooting, had to take time off because of the wrist, and according to Chris Johnston, the team is evaluating options, including surgery to address it. Healthy Matthews was
17.2 and 18.5% the prior two years. He only scored at 2/3rds his normal rate, due to the wrist.
He ended with 40 goals, for the 14th best goals scored in the league. He ended up 22nd in the league for points.
Clearly, this version of Matthews is not top 3, nor really top 5 for C's in the league. If we have a top 15 goal scorer, who is top 25 in points in the league, he should not be getting the top cap hit in the league, nor close. So to me, his wrist health is critical. Do we get 2022/23 Matthews, a top 15th forward, 9th C in goals scored, or do we get 2021/22 Elite Matthews? No team can afford to pay the 14th best NHL players in scoring goals, and 22nd best in points, a top three league cap hit.... and then turn around a attempt to pay one of their wingers, who had the same number of goals, and more points, $4 million less. That just doesn't make sense.
The version we got last year, is a $10 mil cap hit player max, not a $13-14 mil cap hit player.
I truly hope we get 2021/22 Matthews back, and he stays that way, but I don't think we can pretend that 22/23 Matthews isn't also a possibility. 21/22 Matthews is as you describe, a top 3 C and likely player in the league. 22/23 version is a top 10 C, and top 25 player in the league.... How you pay each of those versions long-term, go a long way in determining the success of your team.