All this discussion (for me) involves changes in altitude OR temp individually.
In other words, a change in altitude without a change in temp...which is almost never the case.
Higher alt (by itself) would require slightly leaner jetting.
Colder temps (by itself) would require slightly richer jetting.
But going up in altitude will almost always result in cooler temps.
So the two effects offset each other to some extent.
That is why all professional race teams carry their own weather stations with them...which have temp, humidity, and barometer measurements... and a book with charts so that they just find the current values and read the necessary changes to be made...so they don't have to guess.
The rest of us ride around with jetting that is good (hopefully) for average conditions.. and a little off for unusual conditions.