Sure, the fact that they have two divergent, separate games and are completely unable to move over to the C++ codebase and sunset the Java version due to the lack of modding (I remember the modding community screaming about needing a proper modding API back in the olden days, and Mojang hiring some of the Bukkit team back in 2012 to develop it, and it never came to fruition, still to this day), makes them having to do twice the work implementing stuff, but that's at least parallelizable work. I doubt the same people work on both codebases?
I feel I need to sit down with someone who's working at Mojang and ask wtf is going on over there because it could be fascinating.