Except that the 1965 Missal was in use at Econe, alongside the 1962, based on individual priests' preference, through 1974 ... from the SSPX website itself. I've heard it from other priests who were at Econe at the time that both were being used until 1974, when the Archbishop shut down the 1965 Missal.
Except back in those days the issue was not about whether to use the 65 or 62 missal, the issue was about whether to use the 55, which was what we were using pre-SSPX, or the 62 missal which he had already approved for himself and his seminarians.
Personally, I do not believe for one second that he used both the 65 and 62 at Econe, I'm no eyewitness to this and I could well be 100% wrong on this point, but one thing my memory is very clear is that from the time that +ABL entered the scene, the issue was *always* between the 55 and 62 - for some it's still an issue even today.
From my corner of the world, the 55 missal was the missal that was being used among *all* the independent priests where ever and who ever they were, not just the pre-SSPX and +ABL knew this. It could be (and I like to think) that he had the foresight to know his decision would have a very far reaching impact for a long time on trads everywhere, which was why it took him a few years of thoughtful deliberation after coming to the USA to decide.
In the process of him making that decision official for the entire SSPX, which btw, was really a very, very big deal among the faithful back then, certainly he had to also consider the 65 missal, but that only means that he was comparing 65 to the 55.
Had he thought the 65 was acceptable, he necessarily would have then looked into successively later versions, but he stopped looking into the issue at the 65 because he saw the 65 was no good.