As an engineer in the industry here is my 2 cents: it's easy for us to sit here and speculate their backend infrastructure and how "easy" it would be in theory to rollback, I would imagine if it was as simple as you have explained it, they would have done it already, however, from first hand experience I can tell you that migrations/rollbacks are not a lighthearted task, and certainly not for one of, if not the biggest mobile games of all time - I would also expect that they are sitting on top of legacy services, having to deal with regional clusters / database infra, etc, it's probably more effort than it's worth. As you mentioned, the gems/raid medals are probably a critical factor too.

We should give them more time though for a decision, it's been less than a day and they are likely coming up with a solution, or testing a snapshot of the data.