Personally I don't believe the chairs are a coincidence, they were the absolute first thing that caught my eye in the Direct as they just didn't fit in, and I think we shouldn't underestimate how well Sakurai knows the fanbase. It's not like when you prepare such a big presentation that you just waltz into a room with a camera and start recording just like that either, of course they've set up the room to look in a specific way, and he would know that anything that stands out will be taken note of.
What it means is a whole other thing though, it could be something really minor, or even something that we wouldn't be able to figure out now but might be able to see as a hint in hindsight (like maybe it's related to the Spirits mode or something else that hasn't been revealed).