Does someone have to bring up the example of Jamie Vardy? Playing non-league football until he was 25. Or Kevin Phillips, cut as a youth player by Southampton, ended up playing as a CB for a non-league side when he was 21. Both those guys had no problems scoring goals in the premier league when they got there.
Not that I expect Jones to be as good as them, but you can't write someone off because he hasn't played at a higher level by the age of 21. And the fact that he's still got a contract with a championship club at 21 is encouraging. Most youth players get cut before they are 20. Birmingham obviously think he's got some future there.