I agree that this is the only option left for YEC. It isn’t really surprising. They start off with a non-scientific premise (the Bible is literally true), and then it turns out that none of the empirical data supports that. So, really there is nowhere for them to go other than retreat into a non-scientific conclusion: it isn’t really old, even though it looks old.
I don’t really understand why they don’t take that way out. It would make sense. Why are they so obsessed with having science on their side, if they start out from a fundamentally unscientific position anyway?