When I attached the okkake koma to a drill, the effect was not present. Instead, I saw what I expected: a moving spiral a low speeds that at high speeds becomes just a uniform pink.
I guess the effect must be produced by a combination of the spin plus the wobbling of the top. But I need to further think about it.
I think you are right, the wobble could be responsible for the effect.
I have an idea about it:
I suppose that the wobble is due to unbalance, so that the wobble is synchronized with the spin speed;
If the top spins clockwise, when the stem is moving towards the left, because of the wobble, the figure painted on the stem, (the spiral), will appear to move towards the left faster, because of the combined movements of the spin and of the wobble.
But when the stem moves towards the right instead, because of the wobble, this will make the figure painted on the stem to appear to move slower.
Since the wobble is synchronized with the spin, the side of the stem appearing to move faster is always the same; when the movement appears faster, the white areas of the spiral appear darker, at those heights, and this produces the static rings.
I think that a photo with a long enough exposure, (2 seconds ?), could reproduce the effect.