These are purely my assumptions and guesses, but I believe there is a time-consuming process to get a product released on PSN and Xbox Live and they will have to go through testing etc. before actually being made available. While fixing bugs, you may also cause some new bugs to appear and e.g. cause a product to be less stable - which is fine during development, but might not pass quality assurance to be made available for the public. (Yes, yes, the NHL 19 dressing room still made it through ๐
).
That would be my guesses why the process goes like that. Same thing for when you create a demo of a game that is still in development - you have to choose a build to start working on the demo for, as it is a separate product that will have to go through testing and other processes before release. In the mean time the main product development may be continued with.
Good question. I would guess the control scheme wants to be kept the same between game modes and afaik there are no more buttons available for use in versus. Would be great if you could bind your own buttons to avoid this thing in EASHL, though.