Firstly, I'm sure you could have worked out that "your youtube" was shorthand for "the youtube video that you linked to". Had you even mentioned that it was a Map Men video, I might even have decided to watch it even though I was short on time at the time, but as it was, I just had 5-10 minutes spare before I had something else I needed to do so I didn't even click on it. But even if I had clicked on it, I wouldn't have had time to watch it at the time.

Anyway, I finally found the time to watch it (somehow I missed it even though I've been subscribed to the channel a long time), and it basically agrees with all the points I made, but in a much more interesting way and with additional information. I'm not sure that the tone "you'd know that if you had watched it" was really required, given that nothing that I'd written was contradicted by it, and I didn't really learn anything significant from it that I would have added to my post.

So really, the only thing you're arguing about is the definition of myth. And to me something that used to be true but now isn't doesn't qualify it as a myth [1] [2]. I said exactly that in my post. You'll notice if you re-watched the video you posted, that they also don't ever call it a myth, they say that it is wrong, and later clarify that it used to be true: "So why then do so many people think it's about cathedrals? Because it used to be."

> It is a myth that the former definition of what counts as a "city" still applies to this day, yes.

So no, it's still not a myth, it's just incorrect.

[1] For example "carrots make you see better in the dark" is a myth because it is wildly held, is wrong and has never been correct. Likewise, "the moon is made of cheese". However, "Trump is the president of the USA" is not a myth - it was once correct, but now isn't as he's now just "a president of the USA". Someone in 1920 who'd missed the recent news and said "Women are not allowed to vote in the UK" wouldn't have been repeating a myth, just saying something that was factually incorrect.

[2] I checked a number of dictionaries to make sure before writing this, and while most support a meaning like "a widely held but false belief or idea" when you delve into that in more detail, most dictionaries seem to have the view that a myth has no actual basis in fact, so something having previously been true and now no longer true doesn't seem to fall into the myth category.