Depends on whose war band he belongs to. A small band led by a mega armored nob who isnt quite a boss could easily be filled with orks smaller than say...the warbands constantly fighting the nids. Orks size is all relative. If orks took over a galaxy and fought enough they could probably have an army full of orks almost as big as dreadnaughts or close to that. That would require one hell of an enemy for them to fight against though. Tbh thats what I think the kroks had going for them back in their intergalactic war with the necrons.
We'z gettin' so tuff from all dis fightin'! Or nobz be like Warbosses now, an' oor bosses be like- like .. Well. Dey be wot ever sized ork comes afta da bosses! Supa-Bosses! Yeah, dat works. An' if we are all nob sized- Why's dem uumies stronger dan us! Dey're barely stronger dan da stuntie boyz. I'm sick ov dem boyz breakin' me choppa! Dey don't like da runnin' punch from me nukkles do haha!
That is the proper nob size, and we're just a skarboyz. Start watching from 1:30. That's the nob View: https://youtu.be/_Zvj39JigvU?t=96
Except, Skarboyz are rare outside the Goff clan? To the point that their almost unique to them? According to the Lexicanium page anway.
Rare means something else in 40k than it does in reality. If there'd be 10 billion skarboyz on Arkhona they'd still be rare overall.