The problem with a statement like this and the same goes for dead spots is that just because it hasn't happened to someone else doesn't change the fact that it's still common and has happened to others. You've had 7 or 8 bolt ons in your life and none of them have had this problem while I bought 8 basses this YEAR and two of them had cracked neck pockets. One was used, one was new. I bought a used bass a few years ago. It was around 2 years old and it didn't arrive to me with a cracked neck pocket. After about 6 months of me owning it, it developed a crack on both sides of the pocket.
Just as some people argue that they've never had a bass with a dead spot when in reality they probably just couldn't perceive it when another person might more easily, you might live in an environment where your weather and humidity levels (even just in your house) are more consistent and the wood of the basses you've owned didn't have time to expand. All those basses could have had looser neck pockets. My point being that just because it hasn't happened to you doesn't mean that it shouldn't happen, especially when there are countless threads on TB that prove that it CAN and DOES happen.