The age matters because there's many significant differences between teenagers and a child. The mighty Jason was killed and buried for years by a kid. Something no adult or teen managed to do. If a child can actually kill Jason, then why is it such a stretch of the imagination to imagine teenagers repeatedly stunning Jason?
In fact when in the movies has Jason been confronted by a gang of teens armed with weapons? I can't think of any scenarios. But just because it never happened in the movies doesn't mean it couldn't. Its not doing something that is a direct violation of the depiction of a character, like say the way the game violates the depiction of Roy from Part 5 who can be shot with shotguns and get up and carry on just fine, stabbed in the neck with pocket knives repeatedly and not drop dead, can teleport across the map in seconds, and inexplicably hears Pamela's voice when he had absolutely nothing to do with her.
This game is not trying to adhere to Jason's powers from the movies. If it was he wouldn't be able to teleport across the map in 2 seconds or shift great distances in seconds, or stop cars just by standing in front of them when the movies have very clearly shown him to jump out of the way of on coming vehicles heading right at him. So the big hoo-ha some people make about some teens being able to stun him repeatedly is really inane, IMO. This game is far from being accurate to what Jason can do in the movies regarding his abilities.