I think the article says they just haven't tested other cases. I wouldn't expect the symbiotic microalgae to be that picky.

Edit - The article makes Okkef's point, I just missed it.

Sounds like a solution is still well within our reach. Normally I wouldn’t suggest something as extreme as using cloning techniques to restore wild creatures, but of course it was extreme actions that got us here in the first place, so I think this balances it out.

We could create a bank of coral clones tagged to each individual location.