You've heard of levers, I'm sure. One classic 'simple machines'. Skateboards have more leverage than fists.
This conversation is getting ridiculous.
A skateboard held in your hand can't use much of the mass of your arm to help, it's mostly impacting with its own weight. Your hand can impact with a lot more weight behind it even though the swing radius won't be as big.
How many people, if you asked "Do you have any weapons in your backyard?", would say "Yes, several rocks."
This isn't about possession but about a confrontation. A person with a rock wont get caught by police and taken to court over owning a weapon. But a person swinging the rock around and charging at people will get charged for attacking people with a deadly weapon. And in this situation the question is "Was it reasonable to fear for your life?", then the second definition is used.
And I'll point out that the original post I responded to was saying that they were armed. To me that implies the object needs to be a weapon in a vacuum.