That means the people who have the best information about mitigating this issue have a fix that apparently has minimal performance impacts on their cloud workloads, and I suspect their cloud customer SLO's would be taking a shitkicking if that weren't actually true.
Could Google not just have found a mitigation with non-negligible performance impact, and made a behind the scenes change to the actual hardware resources assigned at each vCPU level to mask the average impact, eating the cost in the short term (while evening it out in the long term by delaying price decreases they would otherwise implement)?
They've had a lot more time with the problem than anyone else has, and billions of dollars to gain by solving it better than anyone else.
If they had a 15-30% loss of performance in their 3+GW of infrastructure, it would almost certainly cause a significant dip in their quarterly results, and they would want to warn the markets about that well in advance to soften the blow.
https://techcrunch.com/2018/01/11/google-claims-its-spectre-...