Sounds like you’re saying those machines executed bytecode.
Otherwise there isn’t a great limiting principle to your logic. Just because someone once built hardware that executes such a high level assembly that the manual referred to it as bytecode doesn’t mean that all bytecode formats are assembly.
Indeed I am, the interpreter is the microcoded CPU.
Even modern 80x86 Assembly is a low level form of bytecode, given that the micro-ops that are processed by the microcoded CPU are completly unrelated to 80x86 Assembly opcodes.
In fact, most mainframes have always made use of microcoded CPUs, with Assembly being referred as bytecode on the programming manuals.
You just need to dive into IBM and Xerox PARC manuals, for starters.