These rigging posts are getting more ridicolous every year. Why would they rig BGs in the first place? Why would they waste resources to keep everyone at 50% in a game mode thats pretty much free to play and has no rewards?
There is this game mode thats called arena. Maybe you have heard about it. If you are good at the game you can have a complete constructed collection just by playing arena. So it would make sense for Blizzard to rig it, so they can sell more packs. It would be actually beneficial for the company to keep everyone at 50% winrate in arena. But guess what? The best players winrate are not even close to 50%. Good arena players can maintain a winrate over 70%. So its pretty obvious that arena is not rigged.
But for some reason they are using some secret code to keep everyone at 50% in battlegrounds. OK.