Thanks! This makes a lot of sense. I worked for an IBM marketing unit in the 1980s so saw some of this up close!
IBM still sells emulators, now software-based, for companies that do mainframe software development. And they are freakishly expensive.
That was deliberate and made a lot of sense. The functionality was split between two programs. The VM/370 part emulates the raw machine. CMS is the "operating system" on top of the VM "hardware".