It's not a matter of whether or not it's a "big deal". It's a matter of whether or not what he's saying can be verified as true. When not only can it not be verified as true, but it can be verified as most probably untrue, then there is reason to suspect that things aren't as they're being portrayed. Sure, maybe poor old Mr. Anonymous just got the President's aircraft model mixed up inside his old failing brain. The problem with that rationale is that it gives us even less reason to believe that what he says is accurate. Then again, he seemed to have recognized the secret U2 and SR-71 just fine. Why I wonder? Maybe because in more recent years the U2 and SR-71 have had more mainstream media coverage than the relatively mundane Constellation. BTW, when Mr. "Anonymous" was allegedly at Groom Lake, the SR-71 hadn't even been designated as the SR-71 yet. It was referred to as Oxcart. So he's obviously filling in holes with information acquired after the fact.
If you want to gloss over these points then go ahead and let it slide. Ignore the fact that it's very unlikely that any CIA/Military man would call just any old plane the "President's plane". In the CIA only aircraft designated as the President's plane are considered to be the "President's plane" unless the President himself also happens to be on it, which he wasn't. The CIA is very picky about these things. Not only that; he didn't just say "the President's plane". He was very specific about it being an Electra. So by saying, " ... it isn't a huge thing to call it 'the president's plane.'" you're actually changing both the content and the context of the testimony in order to dismiss the discrepancy. Sorry Frank, but I don't see that kind of analysis as in keeping with the principles of critical thinking.
And the aircraft discrepancy was just the first hole in his story. Then there is the matter of his "Q" clearance. It's a good thing this interview didn't go into more detail or I can just imagine all the other holes that would start to appear. But then again, I'll admit there's a chance that I could be completely wrong about this guy. Maybe there is really something to his story and I've just turned my "noise filter" up to high? How much would you suggest that I turn it down? All the way to "OMG Aliens!" or just part way to ... what exactly?