I think its important to consider the context, which is clearly stated on the frontpage of Talos: "POWER is the only open, owner-controllable architecture that is competitive in performance".
There are other architectures that could be candidates for an owner-controllable system (see https://www.raptorengineering.com/TALOS/op_twbx86.php for a review of some other alternatives), but POWER8 is currently the one that can be competitive with x86-64 and could realistically build today.
It's called a "Talos Secure Workstation" "designed for security-conscious users." Then they mention the ownership and openness differentiators but nothing else. Other "secure" workstations were CMW's, separation kernels, hypervisor schemes, and so on that protect the system from attack.
So, I think it's a misleading label. "Secure" workstation has a meaning that goes way back. In isolation, it has an established meaning. They should just say open and/or DRM-free as that's intended meaning.
There are other architectures that could be candidates for an owner-controllable system (see https://www.raptorengineering.com/TALOS/op_twbx86.php for a review of some other alternatives), but POWER8 is currently the one that can be competitive with x86-64 and could realistically build today.