I really don't think he believes this.
Agreed. For all we know, we may not have had many midfielders to choose from to bring in. Or we may have been quoted silly money. Also, the Barton factor may have played a part in his decision not to bring someone in. Also, may already have someone in mind on loan once he assesses Barton's fitness and form upon his return.
Look at the CMs he has: Barton, Butt, Smith, Nolan and Guthrie. To anyone outside of Newcastle, they'd say that midfield should piss all over this league.