I teach in a bp/wing setup and haven't experienced any "confusion" from any students. I personally feel it's good for the students to see the different types of gear available to them.
I also teach using a long hose, which I prefer for a few reasons. #1- it's easier for me to hold the reg in front of them while they perform skills that require the reg to be out of their mouth. #2- It shows them another option, and #3- they become familiar with another type of setup early in their diving, so if they were to ever dive with someone with that type of setup, they'd already have a basic understanding of how it works.
In my experience, if the equipment, along with why I use it and how it's used, is explained prior to the dive, or in the briefing, or buddy check, etc. there's never been an issue.