Well he's pretty close to 5M. I'd say he's on par with Brooks Laich who makes 4.5M. And being taller or more physical than another player does not warrant a higher salary. What Bozak lacks in size, he makes up for it in his skill and skating.
Laich is an everyman. He plays wing as well as center, he is a heart and soul guy who grinds out games. He hits hard and is tough as anyone on the ice. He's like their burrows.
Bozak is not a good comparable to Laich. They aren't the same player at all. Bozak may have more 'skill' but he is not as gritty nor as tough, and add to that Bozak has yet to break 50 points whereas Laich has beaten Bozak's career best 3 times. Laich is older, more experienced, grittier, and not injury prone, and thus is worth more money IMO.
Bozak may have a promising future, but as yet he still hasn't proven himself to be a $5m player. A shortened season where he is "on pace" for exactly 50 points is hardly elite, and at 27 he probably isn't going to improve much from here.