Can I confirm my understanding of this bit of road?

https://www.google.com/maps/@51.4843...7i16384!8i8192

Is this unusual (to me at least) road layout simply to allow cars to pass busses at the bus stop?

I went through it late on Friday night and, because the signage wasn't overly clear went straight through the "bus" bit. The car following me went to the right and negotiated the chicane.

Parked within sight of it, every car and van that came through while I was sat there slowed and went through the chicane rather than straight on.

When there's no bus, why don't people sail straight through? Is it that it's often sufficiently busy that you can get caught at the give way? Or is it forbidden to go straight unless you are a bus and I should expect a fine?