Well I think that interpretation would have to come down to a confrontation in a court overseeing the actual regulation, which might not exist, as Data just describes it as a safeguard... its like saying "I'm going to kill you... only kidding" counts as a real death threat.
It's more like saying the first sentence of this dialog
A: I'm going to kill you.
B: I'm wearing a wire.
A: I was only kidding.
counts as a death threat.
By the way, T'Pel's claim about a "security test" isn't even particularly consistent.
Had T'Pel known the test would succeed, and Data would decline to answer, then she would not have given it.
But if she thought the test might fail, then she thought Data might answer. As soon as Data answers, she is in possession of presumably highly sensitive highly secure military information.
So far, Data knows all this too.
But Data also believes T'Pel is about to board a Romulan Warboard in close proximity to the Enterprise. We know Starfleet policy is always to consider the possibility of capture, since we know it is routine procedure to change access codes when officer is captured, as in Gambit.
So, even if Data believed that T'Pel was acting in good faith, he should have known the "security test" was far too risky. Had it failed, and had T'Pel been captured, the Enterprise might be at a tactical disadvantage in a resulting battle with the Warbird(s), and it would compromise Federation security later.
The only way the test would be safe in this context would be if T'Pel actually knew the answer ahead of time. But she never told Data this, so there is no reason for Data to think she knew the answer.
The only way to make sense out of the scene is to assume that when Picard found about the conversation he knew that if he filed a disciplinary report, which was merited, Data's career as an officer might be over. You don't want senior officers with blatant bugs that are so easy to game. Thus, Picard must have deliberately withheld the information from Starfleet to protect Data. This caused Picard and Data problems in Drumhead, but problems of their own making.