Bug in chunk reloading after crashes

Okay, so I have worlds that I've been on for a while and I've gone through a few crashes and none of my builds have suffered from the crashes. What I am here to report is that there are some problems with the chunks that are reloaded after I logged in from the crashes. Take a look at example 1. That's from a flat creative world and if my exploration indicates anything then the chunk generator thinks I'm in a survival world. In example 2 I'm in a survival world and there are large areas of the world missing. You can even see in the bottom left is a spawner that's open and I placed dirt blocks on the side to take a look at it. I'm not mad and the bugged chunks are fascinating to look through but it raises the problems of there being too little room for potential future builds in creative and missing out on resources in survival.