Yes Mike you are right!
Honda raced this bike in Endurance andin WSB knowing that the FIM would issue a new ruling if they were succesful.
Finally FIM introduced a new ruling saying : cylinders must have a round shape!
But Honda had to prove that they finally made the Oval piston bike work, and it was a real wonder!
Just look at the specs:
To give a reference, the 1987 NSR500 specs are the following:
156PS / 12,000rpm
Notice that the HP numbers are almost the same, but of course the NSR is more than 30kg lighter!!
The fact is that there was no other 4 stroke machine that could compete with the NR750 in Superbikes or Endurance, not even the legendary RC30 of Honda.