I submitted a help ticket with Autodesk and have now officially heard back from the Autodesk Development Team:

"The method described is only valid for "inline" equipment like valves and dampers and does not work for built in key components like Bend, RedInLine, RedInLineTee etc. These types are converted using the standard button code mapping. Mapping different bends to different buttons is not allowed, so in a system with a mix of mitred and radius [elbows], this will convert all to one type."

They're going to update their online help guide to say this method only works for In Line Equipment.

Their proposed work around is: "...to use the type selector after the conversion and swap out elements." I think a combination of this work around and the 'Exclude' feature (part of the last subscription) will probably create the best work flow.