It's an instruction set, with an instruction dispatcher, a stack, and a register file. Why would it surprise you that someone would call it a VM?
Are you maybe getting your signals crossed between the kind of VM this article is talking about (in the p-code sense of a VM) and virtualization systems?
Are you maybe getting your signals crossed between the kind of VM this article is talking about (in the p-code sense of a VM) and virtualization systems?