The Amex deal is just a renewal of the existing deal.
Not really grey area, it is explicitly against the terms and conditions of the exec club to sell avios.
It maybe so, but how many people have been cought out? I know someone who bought 300,000 Emirates airmiles for a very low price. If its against T&Cs then why do companies like ebay host such items?
In this person's instance when it was transfered to his account, it was deposited via a merchant chase acc that I'm guessing deals with EK miles.