It could also explain why the prequel Jedi only used blue and green, because those are the only colors found on Ilum. Maybe the prequel Jedi only used Ilum out of tradition, which would tie into their very dogmatic ways and would allow for Old Republic Jedi have more lightsaber color variety.

And like I said, maybe the crystals on Korriban are mostly, if not all red. You could still have the canon “bleeding” method, but it just isn’t the only way to acquire one.

And another reason it makes a lot of sense is because of Mace Windu. Are you telling me Mace was the only Jedi with a personality or faith unique enough to be the only Jedi with a purple lightsaber? But, if purple crystals are very rare and can only be found on a certain planet, it makes more sense as to why he is the only Jedi with a purple crystal (and I think the legends backstory is similar to this idea).