Yes, in many ways that's more apt. Except that the internet tells me it was the FICM (Fédération Internationale des Clubs Motocyclistes) and the ban predated not only the FIM but the world championship.
End of the road for the Velocette Roarer
And so another alternative is the FIM's pesky and short-sighted restriction of the engine swept volume to 500cc when it set up the world championship for 1949. Which I can guess was aimed at filling the grids, keeping costs down and promoting variety.