@Enperry While your point isn't completely invalid - it's an official commercial after all - I'd argue that the clip was made right before or at the start of Splatoon's 'career' as a game, where everything was still uncertain, malleable and hadn't settled yet. But in the last few years, pretty much everyone doesn't pronounce it like in that ad. ^^
Who knows, maybe the person voicing that part of the ad wasn't even given any instructions on the pronounciation?
But in case of inconsistencies between official material, I'd ultimately rely on the pronounciation of the people who created it, and Nogami also pronounciates it like 'platoon'. :D
PS: Not that any of this really matters, but it's nice to discuss these less important things once in a while. ;)