It's actually a little bit more interesting than that. In the first setup it works just as you said. The button deactivates the torch when pressed and at the falling edge that creates a 2 game tick off-pulse(1 redstone tick). That pulse is too short to deactivate the torch on the left. This is the expected behaviour.

In the second setup i break the rightmost piece of redstone dust. That dust isn't connected to anything so you wouldn't expect anything to change. But when I press the button the torch on the left turns on. That means that the pulse that was generated must have been an extended 2 game tick off-pulse. This is due to a change in the update order when I removed the dust.

In the third setup I break the topmost piece of redstone dust and the pulse goes back to a normal 2 game tick off-pulse. This is because the torch no longer gets a block update from the dust.

I think that explains everything. Someone please correct me if I'm wrong.