I don't know...I've never understood the "let's wait for the final mountain stage to attack" tactic and I feel like it is mostly used because of riders not willing to get out of their comfort zone and not because it's a good tactic. Let's say when Carapaz, Hindley and Landa were on their own, Hindley attacks but it turns out Carapaz is actually much better, counters him and Hindley loses a big chunk of time. So what?
If Carapaz is indeed much stronger he will find out on the Fedaia anyway and then knowing Carapaz is the superior climber would only be good for him right now. He would know he can either concentrate on defending or try to attack from further out to catch Carapaz off guard.
But even more importantly, what if Carapaz isn't stronger? I don't know exactly how much Hindley would need on Carapaz to hold him off in the TT but if he wants to feel confident about winning it's probably over half a minute. If Hindley turns out to be stronger than Carapaz what are the odds he actually drops him by over half a minute? People tend to forget how hard that is over one climb. How often do you think the best gc rider managed to finish over half a minute in front of the 2nd best gc rider in last years giro? Precisely zero times. Remember stuff like Quintana dominating Blockhaus in 2017? He finished 24 seconds in front of Pinot and Dumoulin.
If Hindley is actually stronger than Carapaz, by now he has actually made it extremely difficult for himself to win.