I can see that point of view, especially if they actually shipped the product and I decided I just didn't like it after 90 days or something. But in this situation, it was their own fault I had to wait 30 days.
Anyway, I get what you're saying. And a simple solution, if people don't like that policy, is just to not do business with them.
But I don't think it's a written policy/practice. I think they're just clueless about the nuance of handling multicurrency.
At the very least, a full disclosure should be posted somewhere on their page indicating that any refunds issued by crypto will be for the original FIAT price, not crypto! Transparency is key :)