Follow my logic:
The reason a polymer capacitor drifts with a change in humidity is that water is a very polar molecule w/ a dielectric constant of about 80. Polymers are much lower, 2-8 more or less.
Add .1% water to the plastic and you get a large change in d constant, around 4%.
C0G material has a constant that varies but usually similar to water. Add .1% water and you get a change around .1%.
That even assumes C0G will absorb that much water. So the answer is yes, C0G could drift with humidity but it can't be much.
I was reading some papers on plastics, humidity etc. and it sort of came together.
Bob