Actually, no. FWIW, according to this Rubio said "regardless of the veracity or lack thereof of the story....". He didn't say it was untrue, just not relevant to the campaign. Notice, he did not call Trump a liar.
The story was reported as true even in the newspapers of the time and in several accounts. That's why most mews reports dropped the story so quickly, one would assume. Trump does seem to know military history.
Well, his exact words were “it’s doubtful whether that even happened” and “I’ve never heard that story before”, which I’d say is more than enough for Trump to ridicule his knowledge of history with.
It does point out the weakness I think we saw before in Rubio - an inability to think on his feet and another example showing how quickly he snaps back into this talking-points. That whole spiel about the Presidency being a serious job and moving away from “the circus aspect” - I assure you that was a memorized response that he played-back as soon as he could, because that is his comfort zone.