The "non-canon" just refers to the fact that theses Makuta were not mentioned in canon lore at all and hence whoever builds them basically has complete freedom concerning their look and backstory (as long as it doesn't contradict canon lore, of course.)
Since they're all gonna make it into RSG canon they will end up at least as canon+ material, though. (canon+ means they're fit into canon lore as perfectly as possible, but of course are not official canon, since they're fan-made).
Rules and list in post 1
All Makuta are assigned