Steve didn't really mention case makers. Here's what he did say (transcript from Engadget):
Originally Posted by Garz
There's no doubt Apple has cut back (if not completely stopped) providing accessory makers with specs to help them have the products ready near launch. Even if they cherry-pick certain manufacturers and smother them with NDAs, once anything gets near an Asian factory the chances for a leak explode.
10:26AM "When the 3GS came out, we didn't change the design from the 3G. So there were already lots of cases out there for the phone. And more than 80% of new buyers left the store with a case. Now the new phone doesn't fit those cases, and we can't make these bumpers fast enough, so only 20% leave the store with a case... but we're going to figure it out."
The recent Case-Mate story is interesting because the leak came from a well-regarded company's website. They're not some fly-by-night outfit selling stuff only on eBay and shipping from China. But as others have pointed out, those could be for the next iPod touch.
If (very big IF) those do turn out to be for the iPhone 5 and Case-Mate had access to the specs from Apple, that whole "leak" was orchestrated with Apple's approval. Probably because Apple realizes the high chances of a leak from Asia and figured they might as well control the leak for their own benefit. It's very unlikely Case-Mate would risk Apple's ire (and possible lawsuits) just for some short-lived publicity.
BTW, antennagate was blown completely out of proportion. iPhone 4 continues to sell like crazy even after 15 months. Returns & complaints continue to be very low.