Closing as won't fix. The "On gamepad button pressed" trigger runs at a different time to the other conditions (due to the way the engine and underlying API works). When the gamepad button trigger event runs, it is immediately followed by the next event, which sets the "jump" variable to false again. The difference is whether the platform behavior gets to tick between the "simulate jump" action and the next event, which causes it to lift off the floor and makes "Platform is on floor" false.
The "jump" flag is pointless anyway - it seems to try to do the same thing as the built-in "Is on floor" condition, which always correctly indicates the "jump" state even when using gamepad input.