Why are the online releases and volume releases for chapters so different?

So I just finished the Phoenix Man vs Child Emperor fight in the online version (Chapter 100), then read 101, and then I went to continue reading it in my copy of volume 22 which starts at 102, but for some reason the Phoenix Man vs Child Emperor is still continuing? I checked Chapter 102's online version and that version of chapter 102 is completely different from the volume release's version. I'm hella confused right now lol