When working with limited palettes, the artist's decisions are governed by the restrictions, he has to stay within them. You're right, that alone doesn't mean he's creating pixels according to a certain style, he's just adhering to a set of rules. Style comes from a consistent methodology applied regardless of restrictions.
There are several guys whose art I can identify as belonging to them simply by recognizing certain traits present. We call this their personal style. There seems to be two types of style - personal style: defined by an individual's natural disposition to use certain methods consistently in what they do. And then global style: styles probably proliferated by certain artists or groups of artists, practiced by numerous people, all intending to emulate that global style, think of the "cave story style".
Then I guess it would make more sense to call pixel art a genre, not a style. Yet the difference does feel ambiguous even still. Afterall, music has styles and it has genres. And genres have sub-genres. Just ask Helm to list all the metal genres. How did they come about? In the case of metal, certain musicians began to diverge from a defined genre, playing and structuring songs differently, it evolves, and eventually a new genre, or sub-genre, is born. Is it a style or genre, though? When Pantera debuted, they nearly single-handedly made power metal a major metal music type because they did it so well. I like to think that with the changing of the times, they gradually evolved from glam metal (yes, they were glam at first) into power metal. Now, just how does one define when they clicked over into the next genre, once their music changed enough -OR- did their personal style just take on new characteristics, all the while remaining their style?
I guess it's fair to say I am optimizing these images for 2x, but what if I continue to apply the same "optimizing" techniques to everything I do thereafter, that would become my personal "style". So, reasons for the methods are a factor. Dang it's late . . . going to bed