The geometry of the area the bit slots into is different

I believe the difference is that the Philips bit is kind of a star shape, where the blades and the slots that fit together are widest at the middle where they converge, and narrow towards the outside, creating a wedge that ramps the bit out of the fastner. And with JIS they don't narrow, creating a simpler plus shape that functions like two flatheads intersecting with eachother, but with a pointed tip so its self centering

The dot is there to communicate which kind it is since they look a lot like Philips. I believe thats also why posidrive has the little lines- so you can tell the difference. No idea what posidrive is about, maybe its similar 🤷🏻‍♂️

Edit, I was able to find some diagrams attempting to show the geometry differences (sorry, the side depicting each geometry swaps between the two pictures)