The Society for Creative Anachronism has a variety of customs and observances, some following medieval practice and some not. Some were created decades ago on an ad hoc basis by people that were sincerely trying to create a medieval ambiance, but didn’t fully understand actual medieval practice. The inertia of a large organization with decades of history means that many of them will never change, even thought the people involved would do things differently if they had a time machine.
That’s life. If you’re participating with an organization, you need to respect its rules and customs. But from an educational point of view, it creates problems when people see something in the SCA and assume that it’s actual medieval practice. Over time I hope to create the equivalent of an errata sheet for SCA participants, so they can know which SCA practices follow historical reality and which don’t.