Mythinformation is the term used to describe some form of knowledge that is based on apocryphal, false or old knowledge. A play on the the word misinformation.
A classic piece of mythinformation is the belief the Ethernet auto-sensing does not work. The stories of a misconfigured Ethernet ports causing major problems are either mythical or based in the past when there were no accepted standards for auto-negotiation.
The only instance for locking duplex/speed is when using obselete equipment, or when you do not know the configuration of the remote side. In fact, forcing speed and duplex reduces Ethernet functionality. For Gigabit Ethernet particularly, disabling auto-negotiation will almost definitely cause poor performance and outages when the Gigabit Ethernet line gets heavily congested.