xGF% rel. isn't a good measure of defence, but even looking at that the only 5'10 and below D who were below average in that stat last season (in a somewhat reasonable sample) were Zellweger, Grzelcyk and Zac Jones. More than double were above average.
Its totally reasonable to question his effectiveness defensively in the NHL, but that's not the stat to look at. Its far from unprecedented for a player like him to be even more than league average defensively. The question is if Hutson has the skating, hockey IQ and drive to compensate for size limitations. I'd bet all day any day on his hockey IQ and drive, the skating is the question mark.