1st skating as a defenseman is way different than skating as a forward. I know a lot about that because I played defense. A forward plays a 200 foot game. Defensemen play 160 tops.
If you are a defense man and below the blue line on the other side of the ice, you're way out of place. Anything even past the top of the circle is just an area they don't belong.
That's still true in modern hockey, as defensemen aren't nearly as fast as forwards. Mainly because they are bigger. They become defenseman because they can't skate as fast.
Furthermore, skating in defense, when they talk about skating ability in defenseman, is usually lateral and backwards. It's not forward and cutting, stop and go. Which is why fixing defensemen usually has little to do with their skating and more to do with their ability to stay home, know their role, play in their lane.
It's so much easier to be a good defenseman being slower than it is a forward who is slow. Not that you want to be caught out of position because then you will get roasted by faster players and it gets ugly. But having a 40-60 foot head start helps. Their distance is usually reduced to 80 feet or less. As they are already going backwards by the time the puck is going forward. It's when they get caught pinching that things get messy. Which is why good defensemen don't get caught doing that. They have the understanding that they need to be back, in their area in front of the net. Not all over the ice.

I don't put much stock on where guys are drafted or what scouts say as much as what I see on the ice. There were a lot of people, not just me, who thought he should go much lower and guys like Seth Jarvis should have gone higher. A lot of that was based on the speed of their game. There were a solid 10-15 players in the last draft who got real wheels. I'm pretty sure when all is said and done those guys have much better chance of having a major impact. Simply because their speed is just hard to play against. You can't make up for it. The NHL has been transitioning for a few years now. Where the slower players are slowly getting pushed out. It's why you don't see many older players anymore. Guys over the age of 34 are harder and harder to find. What teams got away with just 3 years ago they can't get away with today. Too many fast younger players coming in. By the time Byfield hits the NHL, you'll have had 5-6 years of weeding out slower guys. While I think the players will eventually get a little bigger than they are today, I don't think that will be at the cost of the speed.
They cycle usually goes, game gets faster...player size catches up to game speed. Rinse repeat till you hit an equilibrium. Which looks like guys like PLD, Wilson, Anderson. All fast guys with size.
But you got to have the physical attributes 1st the hockey ability 2nd. If you can't keep up at 18 you'll never keep up later.
And he can't keep up. He was one of the slowest if not the slowest looking forward on team Canada. I just don't see how that is going to transition to top 6.
We'll see in a few years. I doubt he plays next year. But the year after when he's in the AHL we'll get a good idea. Because there will be a speed increase in that game from the CHL.