True. But an untruth always gets started for a reason, whether the reason is malicious, a mere prank, or a simple misunderstanding. The myth (if it is a myth) started somewhere, for some reason. So, where and why was it started?
As I said, more information seems to be called for.
Edit:
I realize that in a criminal trial it is not necessary to prove who DID do the deed; all that is called for is to prove that the defendant DIDN'T do it. (Well, technically, to create "reasonable doubt" that he did it.) But this issue is not a criminal trial, so I really want to know how the "myth" got started if it is indeed a myth.
To illustrate with some other myths:
The myth that the Japanese Zero was some kind of super-plane got started because it really was superior in one very noticeable way: American pilots were surprised and awed by its maneuverability. But it wasn't long before Jimmy Thach and others figured out how to use the Wildcat's strengths to overcome the Zero's strengths, and it turned out that the Zero was not a super-plane after all.
Similarly, it seemed that everybody agreed a couple of weeks ago that Donald Trump "won" that debate because he seemed stronger, more confident, more commanding, and so on, and it wasn't until later that people began to realize that strength and presence are not criteria that are used in deciding who "won" a debate. Somebody who struggles to speak the truth makes a better debate argument than somebody who confidently spouts transparent lies and nonsense. (If this were not the case, Stephen Hawking would never have convinced anybody of anything.) So in both cases there was a reason why the myth got started, even though later evidence showed that the myth was just that, a myth.
So, if it is only a "myth" that the British showed us how to land a Corsair on a carrier (and the OP does present some interesting evidence to support that thesis), how did that myth get started?