There are several reasons why your friend had his account restricted.

1. Investigations on the Ecobank staff (it is against banking ethics for a third parties money to pass through a staff account). Their audit and investigations team may have noticed a trend and the staff is unable to give a satisfactory explanation as to the source of funds (of course he cannot say he is helping a friend wire money).
2. The Ecobank staff will definitely not be in the picture of any request from his bank given the above.
3. Your friend is either not telling you the whole truth. Gtbank has an obligation to inform you the reason (s) why your account is restricted so you can resolve the isssue.

What ever the case, you can call the customer care line and send a mail to their compliance unit for resolution.

Gtbank is the most responsive and responsible bank Nigeria.