They said physical processor. I took this to mean chip. Of course you can't trust chips on the same mother board (there could be a bug where they can read the same memory), so you need a network boundary. So different rack on the server, for each [boundary, however you define that...]

They said physical processor core, and elsewhere just core. That does not mean chip.

Regarding VM/core/chip/motherboard boundaries ...

A number of vexing CPU security vulnerabilities have resulted from a general class of optimizations that share cache resources (memory, TLBs, branch prediction tables, etc.) across different domains, which enables cross-domain attacks.

There is a potential for vulnerabilities even when the domains are separated by a network boundary ... if those domains view the world through some shared cache at the network layer.