Yeah, it varies widely. Most oekaki i've seen displays some, not much, pixel level intent.
Gustav and Flarn draw more pixel-accurate pics.
Several tools are more or less dirty or not according to how you use them. Pep, your example of an airbrush is accurate if you're painting directly on the image. If you're painting on the selection mask, though, you can refine it before laying it down. For instance, i made a good rough of a cloud by airbrushing the selection mask, then posterizing it to 5 levels, so when i filled the selection, it generated 5 colors.
In that case, only the colors are dirty, you can easily control WHICH of the colors is used.
It is similar to lowered-opacity penciltool in that.
..With the palette-map* filter, i am not really seeing a downside to analog-style painting -- you just put it back into whatever palette you want afterwards then tweak. Just have to have an accurate selection.
.. I just used the paintbrush tool to do combination AA and dithering

'Pixel-level intent' implies that you arrive finally at a picture where 95% of the pixels have been personally reviewed. Ergo you can use any tool as long as you finish with its effect under your control.
* it maps the intensity of pixel values to palette entries. intensities [0..255] map to palette entries [0..last_entry]. So it's a combination colorizing and quantization tool.