It DID NOT come with the same software update for everyone. It came with the 6.1.3 software update for a few people, but it also happened out of the blue on other versions, and after upgrading on other versions, and I just responded to another thread where a user reported the problem appearing 6 months after updating to 6.1.3. Plus the fact that if you take the phone to an Apple store they will tell you it is a hardware problem.
There are also a number of posts here (and in other places on the Internet) from people who fixed it by fixing their hardware. The Terms of Use of the forum don't permit a discussion of self-repairs, but a web search will provide lots of instructions on how to fix it by opening your phone and resoldering the WiFi chip, or replacing the WiFi chip. That doesn't sound like software problems to me.
Within the forum there are a number of posts from people who fixed it by freezing their phone, or by heating it with a hair dryer. Heat sensitive software? Really? Again, not a recommended approach unless your phone is out of warranty, but clear evidence that the problem is in the hardware.