He jumped on his friend who the casters said wasn't pixel walking, so I guess it's legit, although I do believe it was a shitty and gay way to play that. LDLC should've won and deserved to win.
The casters were judging based on the proof they had before but since then multiple screenshots have been posted and so on that showed that the guy at the bottom was pixel walking.
Right now most people including casters believe it isn't legit, DHW admins are reviewing it now since LDLC filed a complaint.
So not only lame but against the event's rules too.
And yeah, even to me that doesn't play CS:GO and tagged on to watch, this looked nasty even if it wouldn't have been an exploit. Stealing someone's victory like that is absolutely disgusting.