No, it would only be a bad example by expecting him to produce at Gretzky levels. Which nobody expects because he has never been nearly as dominant at any stage as Gretzky.
The comment was related to size and strength limitations-- which didn't stop Gretzky from being utterly historic in the NHL just as he was utterly historic at every previous level, and won't stop Pettersson from being a very good player in the NHL.
I think that it would be a bad example with regards to either expectation.
It would only make sense to frame an argument this way if you were saying that size and strength has no bearing on the ability of a player to be effective at the NHL level. We know that this isn't the case. The degree that players are able to produce at lower levels is not proportional to their ability to produce at higher levels. It gets exponentially (not linearly) tougher the less IQ you have to make up for it. You can't really accurately scale Gretzky's ability to do it with Pettersson's expected ability to do it, simply on the basis that the reason it might be an obstacle is similar.
A lack of size and strength is a huge mountain to climb and can turn gifted hockey players into useless ones at the NHL level. The outrageous tools and extreme caliber of skill/IQ that Gretzky has is a huge part of what allows him to be completely unaffected by that obstacle, so unless Pettersson has tools of the same caliber, the fact that Gretzky can do it easily is kind of an irrelevant point to bring up (other than as evidence that it's technically possible). Especially when there are players with comparable body types AND skill level to Pettersson that were able to overcome a lack of size/strength, who would be significantly more meaningful indicators of what is realistic for him to do.
Again, I agree with the conclusion, I just think the reasoning is bad.