the Government are not presently convinced
Mr Luff has no need to amend anything - there's the get out clause, already on the record. Simply explained by the fact that further information emerged in the days following the answer ( from 15 Nov 10) has convinced the government that an inquiry is a good idea.
That the new information is nothing more than Mr Luff and the ministerial team at MoD learning that the PM is minded to think an inquiry is a good idea is neither here nor there. Sir Humphrey would approve of the careful wording in that answer...