I actually agree with what the article said, one thing people forget is goku in gt had to tame the beast, but when he was wished to become a kid, he regained his tail thus allowing him full access to the form, in diama yes goku is a kid, but he doesnt have his tail so he couldnt tap into the primal force he needed to be able to do the transformation, so magically assisted transformation would give temp access, but if the wish was to return bodies to the point before the original wish was made, then the knowledge the body would retain to hit SS4 would be removed. So i do see how diama fits in between DBZ/Kai and DBS. Cause when the magic took effect it grew his tail, also SSG when i saw it in super, first thing i felt was it was supers version of a hybrid SS4.