IMHO they screwed other phone vendors more than they did Apple. I don't think Apple would have sold significantly more iPhones than they have seeing as they supposedly sell everything they can produce. As far as actual harm to Apple iPhone sales I don't know there was all that much. Motorola, HTC, LG. . . Yeah they were absolutely impacted on the sales front from Samsung "borrowing".
If there was no competing smartphone product, clearly Apple would produce more phones, and sell them. There is competition in this market, and Apple's limited inventory is due to good planning and sales forecasts (compared to the Nexus 4 rollout that underestimated demand).