Refresher Question Wrong

[PIAA REF]

Number 15 on the IAABO exam seems to give the wrong correct answer (Manybe I am wrong, but I don't think so)

The question is as follows: Substitute B-6 enters the court while the ballis in control of team A and while the clock is running. The officials are inaware that team B has 6 players in the game. B-6 returns to the bench after which team A commits a violation/ The scorer now informs the official that team B had 6 players on the court. The Official rules no Technical foul can be assessed. Is the official correct. I said yes, the answer says no. It sights Rule 10, Section 1 Art 6: Have more than 5 team members participating simultaneously.
BUT, right under that it states Penalty: Penalized IF discovered while being violated.

So how could you have a T in the scenario above.