I think it's more of a 'tomayto vs tomahto' thing...
INS, IMU, IRS, and maybe several more names for the inertial reference that provides acceleration and re-position (somebody has to provide it with an initial position...) data to the navigation system.
Current systems have many more inputs and outputs than the older ones, and use fewer moving parts to do essentially the same thing, better.
Call it what you want. I think the common word will still be "inertial."