This all makes sense to me when I see it through the prism of comp for their labor. If Baseball were to take away the ball-strike responsibility from the umpires, which is probably the highest-level responsibility they have currently, an argument could be made that umpires would not need as high a level of proficiency to do the overall job, which could lead to accepting less-experienced umpires who could work for cheaper, which could work to being down overall comp eventually.
It could be fairly counterargued that the umpire’s union would protect the high comp level for their members, and I could see that being the case for this and maybe the next contract, but over time, the reduced need for highly-proficient umpires may work toward bringing down the overall quality needed, and the comp down with it.
All speculation, of course.