I have just done a test by replying to email I sent myself, I saved my reply as a draft and then when I go into the drafts folder to pull it up, as you mentioned the original email is not shown, but the original email is included when you send it.
I have a Samsung A (2017) phone and using the Samsung email app I have tried to reply to an incoming email but it goes into the draft and I get an hour-glass busy signal. the email won't send.
