So after talking to Shearwater in detail and using this recently on multiple dives in Cozumel - it is a NON ISSUE unless you violate DECO.
So you can set up 3 gases for REC diving (21/32/36) and switch away using the quick change gas menu between dives. Worked flawlessly for me as I never broke DECO or got close. Would dive air 1st dive, and during SI change to 32 or 36 and then back again next day for air.
Loved how easy and simply it was vs any other computer out there.
This is what I have experienced in regard to gasses that are turned on but not used in Rec conditions.