It's really a pity that the term MUI is now used as abbreviation for Modern User Interface. It has been used by Microsoft for years as abbreviation for Multilingual User Interface.
Not only that, to me MUI just sounds "techy". Most of my customers love me because I try to never speak tech to them, I try to make it as basic and clear and as understandable as possible what I'm talking about.
It's confusing enough for Windows 8 noobs as it is, differences between Desktop and Modern apps and Desktop and Start environments. Talking about a "Modern" app or environment means a lot more to them than MUI.
Just my .02., feel free to carry on however you've been doing it!