It makes zero sense I agree but I don't think Hughes will not want to extend him.
I suspect Matheson will sign an extension for three years as a 32-yr-old past February next year. Somewhere around 3.5M like Savard had gotten, maybe 4M because Matheson, compared to Savard can actually skate.
I think it actually would make sense on some level:
Next year, another year where winning a Cup is an impossibility, Matheson can serve again as a stop gap-solution in the top-4, with Hutson playing on the right side alongside Guhle that would remain on his natural side, as we saw for short while near the end of this year. Reinbacher, or Mailloux, can get an audition on the third pairing (I'd play Mailloux, to see if he can stick in the NHL and let Reinbacher play a full season in Laval to get stronger and try to put his knee injury behind him.
Matheson - Carrier
Guhle - Hutson
Xhekaj - Mailloux/Reinbacher
Struble
Come playoff time, if Reinbacher gets called up at the trade deadline, and Mailloux plays wellenougsh as a 3rd pairing D, the D-Corps picture would already potentially become radically different and Matheson could start taking on his future role with the Habs.
Guhle - Carrier
Hutson - Reinbacher
Matheson - Mailloux
Xhekaj - Struble
The following season (first of Matheson's extension), Matheson could be part of a mobile 3rd pairing and play the same shutdown role he had played with Carrier as a stop-gap the previous season:
Hutson - Reinbacher
Guhle - Mailloux
Matheson - Carrier
Xhekaj, Struble
Matheson's smooth skating style should age well as a 32, 33 and 34 yr-old. He'll be 35 by the end of the last season in his future 3-year contract.
He would be useful as protection in case an injury and can also serve as a tradechipin the last two seasons of his future contract.
It would also keep Xhekaj in line as a depth D and reduce the cost of a future extension for him with the Habs. He can find a full-time spot in the lineup once Matheson moves on. Xhekaj would be 27 or 28, more mature and in his prime as an NHL D when Montreal will start competing for a Cup..