How hard is it to anodize 7068 Aluminium?

I do not agree.
the aesthetics of a yoyo is an important thing and given the sales prices everything should be perfect, including staining.
defects in coloring, unlike those of vibration / processing, are easily solved, once identified the faulty parts to them can decolorize and re-anodizing again … if it is not considered convenient, they are sold as a b-grade at a reduced price … as it always has been.