Justification is actually a sore issue with the Kindle (at least after Kindle 1). In Kindle 1, there was an option whether you wanted left- or fully justified text. Since Kindle 2, all text is forced as fully justified unless the coding enforces left justification.
If I remember correctly, I wanted to test people's preferences regarding the justification, and one or two of my Bibles enforce left justification. You are the first to say anything on the issue for my Bible editions. There is no easy way to switch justification without reconversion. If there are more people that prefer fully justified text, I'll do that as a default.
See more discussions about justification on the Kindle here:
https://www.mobileread.com/forums/showthread.php?t=51582
https://www.mobileread.com/forums/showthread.php?t=88073
https://www.mobileread.com/forums/showthread.php?t=59512
https://www.mobileread.com/forums/showthread.php?t=66340