A lot of what passes for gospel in climbing is based on the untested or anecdotal.

Things like connecting two loops of cord. In the old days we did a strop hitch or girth hitch and thought no more about it. We just figured any knot would reduce the strength of the cord by up to half. Since we overbuilt everything in the first place, no problem.

Now, I get told when connecting two loops of cord or web to use a carabiner, that it is much stronger. (Bull pucky, it is one more thing that can go wrong, either by the added chance the biner is damaged or by getting cross loaded, and it uses up one piece of gear you might need later on the climb.)

All that because John Sherman reported a girth hitched sling broke at low load.
Suddenly girth hitches are only for connecting a leash to your harness. (If they are not strong enough on one piece of an anchor system, how in heck are they okay as your ONLY connection as a leash?)

This supposed new safety rule is still being passed about years after tests showed Mr Sherman's broken sling had been badly damaged beforehand.