When connecting a duct with a duct connector that happens to be close to another duct connector(s) - e.g. mechanical equipment or air terminals - , Revit gives us the option to choose which connector we intend to connect (first image), which is very useful given that different connectors can present different characteristics.
However, the same won't happen when connecting flex ducts, which would be very useful given a large part of duct connectors are ideally connected with those.
Thank you.