Curious Question: What would be some applications for the Reverse Belt?
The use cases are maybe a little marginal. It's useful if you want to make a manual splitter that is controlled by logic, or if you want to make a system that stalls the items for some time before letting them through.
It is also useful if you are making an automatic rocket network. Silos are always A to B because you can't change their target, so the only way to dynamically change the target of a rocket is by using a reverse belt to choose which silo it goes to.