Taleb happens to repeat the butterfly story uncritically, I thought it had been debunked as urban myth
Not sure what you think might be myth, but the butterfly effect is an analogy that used by the discoverer of Chaos Theory in, I believe, his seminal paper.
And the effect it describes is no less true now than it was then - some systems amplify miniscule differences so hugely that it is inherently impossible to predict outcomes usefully far into the future.
So there are no myths that I know of associated with the butterfly effect as a general thesis - unless you were referring more specifically to something like the butterfly effect on trading.