User blog comment:Marco the Marine Admiral/Theory: Evilness Can Lead to Power-up for Dragon Slayers/@comment-24748439-20140629210700/@comment-7418318-20140629230327

Dragon Force gave Natsu and Wendy a massive power and speed boost and even the Twin Dragons got a lot faster and stronger.

What Cobra and Laxus got was nowhere near as significant and thus more along the lines of White and Shadow Drive.

Also everytime that someone was confirmed to go into Dragon Force the story made a really big deal out of it, but when Cobra and Laxus went into this mode, whatever it may be, nothing was said about it.

And the wiki policy also plays a big part. It was not proofen that this mode of Laxus and Cobra was Dragon Force, so we can't call it Dragon Force in the articles. That'd be speculation.

Of course with there being neither proof for nor against it, you can believe whatever you want, but the last time this was discussed, the majority of people seemed to agree that what the 2nd gen DS went into was not "true" Dragon Force, so some people have taken to call it "fake Dragon Force", just like Laxus was called a "Fake Dragon Slayer" in the story.