Seems very plausible, considering all the other rumors...
yep it is plausible that
1. somehow this person got a real backplate intended for actual production which has perhaps already started in order to have enough product for a huge launch sweep like the new iPad had
2. somehow this person got a prototype backplate that was produced in a very limited run that will end up being yet another rejected design
3. this person has seen on the rumors, creates unofficial back plates already, mocked this up from the rumors and is trying to pass it off as legit.