While I was experimenting with the Bit Splitter Wire it didn't behave like in the Documentation (or I did something wrong).
I seems like it acts like a normal wire.


I think my setup should always output 0 but is just tunnels the 2 active bits trough without any manipulation

In your setup the cables and the the bit splitter are still connected to the same shared signal network, so the signal directly travels from levers to display effectively ignoring the bit splitter.

However I fixed that now so the cables (and bit splitters) are automatically disconnected from each other when one of them gets the connected face set to Redstone input / output. And that will conveniently also set the connection of the other wire to the matching opposite transmission direction.