That is all that I was saying. Going back to the OP, you can't guarantee that you are going to be able to use it. I was stating what is says for the sake of an argument that Disney "has" to let me use it. When they don't have to at all. am I wrong here?
You CAN guarentee that BARRING EXTENUATING CIRCUMSTANCES, you WILL be able to use a late Fastpass on the same day. You're correct, insofar as if the Fastpass line is backed up and your time is expired, the CM can ask you to come back later. But if the line is a normal length, the CM HAS TO take the last Fastpass as a matter of Disney policy.