I think this may be very true. I only use BT with my 810 to either get a course onto the 810, or to the save a ride after. In all cases BT has worked with maybe one hiccup in 16 mos.

Thing is, I never glance at the screen that has the satellite or BT icons while riding, so might never know if BT to the phone has dropped. Not sure it would warn me when I am on the primary data screen. And since the saved and uploaded file always works....