The EAD is given while the Green Card process is ongoing. This could mean that the devision has not been made in your case, yet. Your getting EAD after 10-12 days of interview might be coincidence. When you apply for GC, you must have filled a form for EAD, they finally sent you the card.
In any case you can check your status online.

Disclosure: I am not a lawyer and I suggest you to either call a lawyer or call the visa case status number to find out more. My opinion is merely a speculation.