My money is that this is all about the scoreboard. AI stats and scoreboards can't live together. I reckon this is prep for giving you want you want.
Not 100% sure what the journey Dice were going to take us on, but I think the apparent popularity of the scoreboard might mean we will never get to see it.
It has various simple solutions - let's not display bots on the scoreboard at all or mark them clearly, put there some filter and so on. But I guess PvE players aren't much interested in a global scoreboard there anyway (I certainly do not care about it even in the multiplayer, the current solution is entirely sufficient to me). But the scoreboard present or not, it's not a reason to disable the progression there entirely, two very unrelated things (as the weapons, etc. progression isn't a part of the scoreboard and you can still get XP in the solo/co-op - if you meant the stats gained from that mode).
