I wouldn't read to much into this. The Bengals often bring guys in for tryouts. I think in Bengals.com there is an article stating all the guys they was brought in for workouts during the season, and they signed zero.
Even then, there are worse backups out there. Look at Philly. I saw McLoser in Detroit. He blows. In college he struggled to pass for over 50%. At Rutgers no less.