Indeed. We have a few zEnterprise systems in our corp data center (geeky enough looking that I want one in my basement), running with 5.5GHz chips. https://en.wikipedia.org/wiki/IBM_System_z
Exactly, this is the first ever 5GHz x86 chip. The title is factually inaccurate.
That's not surprising, given the title comes from and links to a press release.
They didn't ship the first 64-bit CPU to run Windows either. Windows NT ran on Alpha (among other architectures). Granted the OS was still 32-bit, but the CPU wasn't.
But what do you expect from a press release? It's written by marketing trolls, not engineers.
AMD literally defined the 64-bit x86 architecture that everyone (including Intel) uses today.