I can't reproduce this. Note that in the reproduction steps #2 is unnecessary. Instead, the result of drafts.create() in #1 should be analyzed, the id of the new draft message is present there.
Also worth noting, Draft IDs are not the same as Message IDs. The response of drafts.create() and drafts.update() will be a Draft ID while the result of drafts.send() will be the message ID. When viewing the sent message in Gmail UI make sure you are using the message ID.