(my feeling) is that the point of Gridfinity is that it is an open standard, so the creation of different grid systems is not what I think most people would have in mind when considering “Gridfinity”. The question I had was really if the Gridfinity “system” or more accurately the specifications for the base grid and associated bin features, would be a copyrightable thing, if the original models are not used to directly make a Gridfinity bin or grid as part of something new (like a Gridfinity bin which holds 21 silly straws or something like that).
I also just want to note that the issue I had with the Etsy seller was not gridfinity related.