Uhm... I'm gonna go with "No".
First of all, that article is, not to put too fine a point on it, garbage.
Secondly, just because a weapon
can be used for terrorism, that doesn't mean that
all uses of said weapon are by definition terrorism.
If you fire a gun at a firing range, that's recreation or practice.
If you fire a gun at a tree on somebody else's property, that's vandalism.
If you fire a gun at a crowded town square,
that's terrorism.
Likewise, if you DDoS a server used for sending phishing mails to innocents around the world, that's vigilantism.
If you DDoS a gaming service, shutting it down for a few hours, that's vandalism.
If you DDoS an air traffic control network,
that's terrorism.
So, is DDoS'ing a gaming service just for the hell of it a nice thing to do? Of course it isn't.
Should the offenders be punished? Why, naturally.
Should they be tried as terrorists? Hell no.