Anyway, he had an additional thought.
It is in the scene with Gibbs and Jenn in her office.
And it's the bit where he asks if she's worried whether he'll flunk the Psych test. And then goes on to add 'or the firearms test'.
J says that the way the said that was really barbed and he believes that it meant something, something pertaining to Jenn and Gibbs's history. We all know that Gibbs is an ace shot, and Jenn knows that too. So why did he say it? Especially in the one he used.
J wonders if, maybe, Jenn nearly flunked (or indeed did flunk and Gibbs covered up) her firearms test (we know she threw up at her first autopsy), and whether it is linked with the shooting in Paris.
As soon as J mentioned it, I agree the comment was barbed, most definitely so. And there was no need, no need at all, for Gibbs to mention that. There could never be any reason to think or even hint that he'd flunk a fire arms test.
Thus, I agree there was something behind it.