[Oz]

...Is this normal? Temperatures were pretty low, and the altitude is definitely up there. So O2 levels are down.

Just a quirk of a single, or do I have an issue needing to be fixed?...

Not a quirk of a single and no, you don't have an issue that needs fixing.

While a modern fuel injected bike is running, oxygen sensors send data to the engine management system to control the air-fuel ratio. This feedback loop delivers the correct fueling regardless of air density changes from altitude and weather (temp and humidity).

Your bike is set-up to idle and run at a specific altitude and then it will adjust from there. Problem is it was not set up to idle and run at 14,000 feet. That's why you had trouble restarting it at the top of the mountain. Once running, the engine management system will adjust for the altitude and weather.