It maybe is (becoming) standard, but 8GB is still base and this is, for example, what my local store has right now, for both the 13 and 15 inch M3 MBA. They have 16GB options listed, but those are currently unavailable and no custom configurations are offered. Base configs are always available, hence my comment that upping the base RAM would make certain that people who want or need more RAM have access to it.
In any case, it is definitely positive that Apple is moving in the direction of stocking higher RAM configs, but we'll see how that spreads worldwide.