Don't the industry labs have bigger machines by now? I lost track.
As others note, these systems are measured by running a specific benchmark - Linpack - and require the machine to be formally submitted. There are systems in China that are on a similar scale, but, for political reasons, have not formally submitted results. There are also always rumors around the scale of classified systems owned by various countries that are also not publicized.
Alongside that, the hyperscale cloud industry has added some wrinkles to how these are tracked and managed. Microsoft occupies the third position with "Eagle", which I believe is one of their newer datacenter deployments briefly repurposed to run Linpack. And they're rolling similar scale systems out on a frequent basis.