This is called a “Cluster” and it precedes Linux by a decade or two, but yes.

And what else would the supercomputers run on? Windows? You won’t get into the tops if half your computers are bluescreening while the other half is busy updating…

The times when supercomputers were batch-oriented machines where your calculation was the only thing that was running on the hardware, with your software basically including the OS (or at least the parts that you needed) are long over.