The revision is a separate thing from the appeal.
The appeal takes a long time to set up, so you get plenty of time to get your evidence in, but the DWP can get on with reviewing its decision straight away without waiting for all that evidence.
There's nothing to stop you giving them more evidence and asking them to take another look, but in the meantime, their having decided on the basis of the evidence they have so far not to overturn their decision doesn't mean that the evidence you submitted will not be considered at tribunal.