While they haven't shared details of the foundry process, they apparently get the chips back in 4 weeks. So the 15 week minimum thing is old news now.
Even though BFL is known for delays it's quite likely this will also happen to their competitors. Look at Hashfast for example.
Bullshit.
Post your references that makes you believe it is 4 weeks, otherwise I call Bullshit/False hope.
There isn't a single manufacturer out there who can have their chips pop out of the factory in 4 weeks. Especially at 28nm.