Comment by bsimpson
Looks like a new controller attachment system, maybe magnetic, except that doesn't seem robust enough for excited play.
I wonder what that means for spare controllers. It's a waste to make people go buy new extra controllers for multiplayer games. Maybe you can use your old Switch as a charger and pair via BT? Not nearly as nice as just sliding it on to pair, but hopefully reduces e-waste.
I would be surprised if older joycons can't be paired via BT.
There are already alternative ways to charge them, either charging stations or charging grip.