[riskable]

The trouble with "secure CPUs" is that they really only secure the boot process. It is then up to the OS (as usual) to secure itself which is where most failures of security occur anyway.

Consider all the phone "OSes" (aka ROMs) you can install on phones with locked boot loaders that just replace a few binaries/files here and there in an existing OS to change how it works/feels. The maker of said ROMs may not have the ability to replace the kernel but any vulnerability in said kernel will allow them to replace everything else which is precisely where userland security lives.

So the hardware may be "secure" from the perspective of the manufacturer but not from the perspective of the user. They can still be pwned.