I tend to give a bit of room for these things.
When I bred tropical fish for a living, many of the things considered wives tales among a lot of breeders for sexing were in fact true. It just took a lot of observation to develop the eye for it.
I had about a 90-95% "accuracy.
But there were subtleties within those observations that were hard to fully communicate.
And I had some breeders that insisted I was just a damn lucky guesser.
But I never had a "matched set" (different than a "proven pair") returned to me, so I never took their bs to heart.