3d printed threads and snap connectors are nice, but M3 bolts and nuts are more robust and look dope. They also make the model easier todesign print, since you don’t have to worry about tolerances as much.
STEP/STL and instructions available here: www.printables.com/model/548770-master-spool
I think it’s more of a replacement for plastic spools, since cardboard doesn’t work well in edge roller spool holders and master spools are almost always reusable plastic which does work in edge roller spool holders. If your spool holders work with cardboard rims then yeah there isn’t much of a reason.