...although they really did, the vintage equipment simply could not reproduce it.
That's my point, exactly - it was already signal information captured by the microphones.
What a microphone emulator
can do is analogous to "false color" photography - it can "color" the sound by re-mapping the frequency response - effectively EQ - that can boost or lower particular frequencies in ways similar to how classic microphones respond.
But if you microphone is deaf to certain frequencies or detail, it's not going to be able to recover signal information that was never captured in the first place.