> Which means grid operators can ask them to disconnect quickly

Really, now? Yeah, they can ask, but do data center operators just go "oh grid needs our power! Let's switch to backup!"

That seems unlikely. Why would a data center (or any large consumer of electrical power) be forced into a backup/contingency plan, when no crisis exists at all? Other than drilling/practice runs, I cannot see them readily agreeing to this. Is it actually a routine occurrence?