Derian Hatcher has a specific idea of how he wants his team to play. Chychrun has bought into that mindset really well.
It used to be that Sarnia was the epitome of a "junior-style" team, where offensive players cheated for pucks and the biggest talents had free reins to play however they wanted, as long as they scored. It was one of the biggest reasons why NHL teams didn't take to the Sting program as well as they did to other franchises, despite some big-name prospects coming through their system in recent years like Stamkos, Yakupov, and Galchenyuk.
It's one of the reasons why Pavel Zacha wasn't putting up big numbers last season, IMO. He's a smarter player than people give him credit for, but when his teammates are roaming around wildly and with no structure, it's hard to develop chemistry with them, forcing him to play a style that doesn't suit him. He's not like the aforementioned 3 in that he doesn't have the kind of skating burst that allows him to go out and score despite his team, he is at his best in a system that allows for a strong cycle game and controlled offensive zone time. Which the Sting have never really had.
Hatcher was brought in this year to change that, and so far it's worked wonders because the team is far more competitive as a whole, and a lot more balanced down the roster. Chychrun's game is different from last year where he could go out and do whatever he wanted, it's a lot more controlled and structured. He has the talent to play a run-and-gun game but Hatcher was a defense-first player and if you want ice time as a defenseman under him, you'd better make sure to protect your own turf first.
Chychrun was never going to look like Sergachev or Juolevi under Hatcher because the other two play in a more open system and have more of a green light to take chances, but I think his transition to the NHL is going to be easier. He's shown he can be a force, but also that he can play a safe, reliable game. That'll help get him minutes in the NHL.
I think he still has number 1 upside, he hasn't shown me anything to suggest that he can't play 22+ minutes in the NHL one day. He's the best defenseman on the Sting, and the go-to guy in all situations. He still has an amazing ability to move the puck up the ice. Doesn't have any major weaknesses, besides the fact that his current production isn't matching up to his talent level.
If guys like Ekblad and Chychrun were only dominating with physical ability, I would be worried. But these guys are elite junior defensemen while playing a more cerebral game than most people expect out of a big player. They have the ability to assert their physicality but they just don't need to most of the time because they're smart and have an excellent grasp of the fundamentals. The physical aspect is a secondary fallback, which suggest they won't be struggling with bigger players when they DO need to use their bodies.