I've got no proof to back up this story but my experience of this was definitely true.
Back in '84 I bought the first Ninja 900 that came to my area. It was the first anyone had seen at that time. It's VIN showed it to be very early build date.
The competition at that time was the Yamaha 1100 aircooled bike (can't remember the name) that was faster than the 900 according to all the magazines by a fair amount but these were the two hottest bikes to be had back then.
It had a recall on the rubber diaphragms in the carbs so I took it in to the shop to have it done and the head mechanic took it out for a spin with my permission.
He comes back in with the rotors blue and a big grin on his face saying that my 900 was way faster than the Yam 1100 that he also sold ( again this was not supposed to be true but was apparently). He was truly impressed and puzzled by this.
Sometime a little later I did a valve check and found that I could not get the hash marks on the cam sprockets to line-up correctly, cam timing was hand set differently than other bikes of the same kind. I then checked further and found that quite a bit of hand polishing had been done to the intake tract as well.
All I knew at that point was that I had a 900 that would eat a 1100 alive and a lot of custom handcrafted minor changes to benefit performance that were not done to any other Ninja 900 we ever saw ???
Never did figure out what was going on but my friends and I finally decided that I had a "press bike" that was destined for the magazines to report on (due to the very early build date) but was never released to the press.
Now if that was true then that was kinda chicken**** on the part of Kaw but the other brands probably did the same thing. This sort of thing may still be going on but on the other hand the early H-2 (2 strokes) came with bigger carbs initially but later in production Kaw gave them 2mm smaller carbs to tame the beast a bit. (chains and tires back then could not cope with big power).
Still have that bike.