As the screenshots below show, Microsoft considers the Intel Pentium 4 661 a supported processor. Intel released the Pentium 4 661 in early 2006, with a solitary core to its name. Apparently, Microsoft forgot to add any Intel Family 15 (Netburst) SKUs in its unsupported processors list for Windows 11.

Hence, the PC Health Check tool sees that the Pentium 4 661 has a 3.6 GHz boost clock, which satisfies one of Windows 11's requirements. Curiously, the tool states that the Pentium 4 661 has two or more cores, even though it lists it as having one.

@Carlos_SM1995 has even got Windows 11 (Build 22000.258) running on a Pentium 4 661. Supposedly, Windows Update still works too, highlighting the ridiculousness of Microsoft's overtures regarding Windows 11 compatibility.