The article http://www.nachi.org/dryer-vent-safety.htm statesL
“vent hardware is available which is designed to turn 90° in a limited space without restricting the flow of exhaust air.”
What type of hardware does not restrcit airflow? Is the article referring to a regular elbow, or something else?
IMO… you’re reading it out of context. They’re not talking the technical engineering, but the functional traits… NO kinking i.e. restrictions…
For one example… think “In-Wall DuraVent Periscope”…