I have never heard that, and I had no difficulty in keeping a good GPS signal when I was bike touring in Iceland which was just a hair south of the Arctic Circle.

I am not sure but I think that you could loose WAAS if you are farther north, that could impair your accuracy and precision.

The Op mentioned iphone, which of course uses different apps than android devices, but on my android phones I found this app was very good at telling me which satellites are up there.
https://play.google.com/store/apps/d...tcross.gpstest

On my Garmin recreational grade GPS I usually put it in battery save mode, turn off WAAS and Glasnost to save battery, that impairs my precision somewhat and makes getting a GPS location slower on start up, but otherwise it is pretty good. But I use a recreational GPS that has a very good antennae, Garmin 64, see photo.