Now add in hypothermia, noise, weather, or bodily harm to that equation.
The only improvement would be if the app could provide the NATO phonetic alphabet version of your coordinates to you - but you're not going to remember those without looking at your screen while talking - which is multitasking in a situation that you probably aren't going to do it well in.
Finally, the verbal transfer time is about 1/3.
I don't like this thing for the reasons provided (proprietary and clearly has issues), but would rather see this in use than trying to provide ten numbers while bleeding out.