“How is this different than diesel electric propulsion?”
Beats me. I just assumed it was just another reference for Diesel Electric.
I get confused sometimes when one industry calls something one thing yet another industry calls it something else. Railroads for instance use Diesel electric, but perhaps the military, or the ship building industry calls them IPS. Of course then the submarines use Diesel Electric, so maybe it’s something else. I don’t know.
I did searches on IPS and it seems to apply to more than one technology.