The casting director will still be the one doing the day to day process of talking with actors managers etc I believe, but yeah for JB the casting decision is probably with the producers at Amazon

That's your mistake right there: thinking that the drooling masses need a plot. Just make some things explode, others move fast, and some be sexy to look at and you've got yourself a blockbuster.

By which I mean a hit movie, not an almost entirely defunct video rental business.