I have the same thing on one of my upper east facing windows in my office.
Linas is correct.
#1 Condensation is relative to the temperature of an object subjected to outdoor ambient conditions above the dew point temp of the object that is getting wet.
#2 Why is it one and not others?: When you begin to “think thermally” as Linas is, there are many conditions not obvious to you that can drop the windows temperature colder than the outdoor air.
Why does frost occur when the temperature is not below freezing?
Why does one side of your truck windows frost and not the others?
Look in your first pic.
See the reflection?
That is a hint.
Now, the windows “perspective” may not be the same as yours. So even if other windows can “see” the sky, it may not be the same.
Why the East side?
That is where the sun comes up.
Heat drives moisture.
You can not see or feel this stuff.
But it can be measured.
Those that think they can find stuff without Thermal Imaging can chime in now with their undocumented opinion.
When you changed your windows to a better thermal rating, it allowed the window be colder than your old ones and now you see proof that the new are better than the old.