Cloud providers (and everyone else) are unfortunately always downplaying their incidents though, so I don't trust that information. I have no idea about this particular case though since I'm not a GKE user.
Would be interesting to hear from actual users how serious this is.
I run GKE clusters in europe-west2. Completely unaffected. I run on the latest k8s version. I have an uptime monitoring service which runs in AWS and it reports zero downtime over the last 24 hours.
We're using their "stable" release channel which means most of our clusters are currently on a version of 1.25. We only have a few deployments using PVCs so impact is pretty minimal anyways for us as far as I can tell.
Even ignoring the fact this only affects one old version and Google makes it very easy to upgrade (and know when you're behind), I can't imagine this is affecting many workloads. The vast majority of the workloads I run (and I think get run, generally) don't rely on PV's. Then from that, most of the time you're not making wholly new volumes all the time you're generally just consuming the already existing volumes.
Would be interesting to hear from actual users how serious this is.