If it has the attributes of pixel art then yes, be that pillow shading, dithering etc. The size doesn't matter, the way it is produced (by hard edged brushes pixels) and the overall style is what makes something pixel art. Not the size.
I consider it a medium, or at the very least a specific way of approaching digital art. It's drawing pixel-by-pixel. Just like pencil drawings are probably restricted stylistically (e.g. no color), pixels do have a tendency to have a certain quality.
If we're considering the tools used, then I still think that pixels can be called its own medium. Pixel art heavily relies on the 1-pixel pencil tool, but anything else that doesn't come with automatic antialiasing is totally fine but not as much. Other 'styles' use totally different tools.
Besides, I wouldn't wanna be stuck calling myself somebody who's mastering the medium of computer mice. I personally find it more convenient to think of pixels being the medium.
Plus, an art style to me, is all about the end results. You can use the exact same tools with pixels but create totally different results. I believe calling pixel art a style is misleading because the possible art styles that are totally feasible with pixels are too great.