I don't really see the logic in this. It seems like the typical workflow they're imagining goes something like:

  1. Compose email to A-list investor
  2. Hit send
  3. Realize that you forgot to attach the deck
  4. Kill self

So now they're trying to make this the workflow:

  1. Compose email to A-list investor
  2. Hit send
  3. Realize that you forgot to attach the deck
  4. Hit undo and fix problem

All well and good, but step #3 requires you to look over your email and realize you made a mistake. Why not just do that before you hit send?