Hi Font,
First sentence not true.
Second sentence, not overly important whether that's an accurate statement or not. Give me a fly that catches trout when I select it and I'll be glad to catch a sufficient quantity of fish so that I have to change to another of the same. I mean really. If we both use the same pattern and you catch a dozen on your one fly and I catch a dozen on two flies (had to change per your rationale) I'd call that a great day for both of us.
Regards,
Allan