I don’t really understand the argument against refunding it. It was changed, and pretty significantly. I don’t see the point in some arbitrary bar/rule that never existed before being applied here.
That reluctance would make sense in a situation where a character and the ability in question had been around for a long time and it’s usefulness was already waning. In that case, I could see the argument that players could be trying to take advantage by re-using those ability mats elsewhere.
That’s not the case here. Omi’s are pretty new and there aren’t a bunch of new ones overshadowing it.