Good info on the humidity inside and out. With a 90% level, you can be sure the quilts were loaded to pretty high.
The temp difference, inside to outside, of the quilt will force it farther out in the quilt.
If the temps are colder than freezing inside the sock, there will be a "frozen" line in the quilt at the temp change area, holding the moisture there, and eventually causing wet out of the insulation.
Not a big concern for an overnight, if you can dry stuff out daily, but on a longer trip can be a real issue.
Venting is VERY important, to carry off the moisture laden air.
Using the frost bib also forces the breath moisture to one end of the sock, which allows the quilts to exhaust the moisture easier.
Life's A Journey
It's not to arrive safely at the grave in a well preserved body,
But rather to skid in sideways, totally worn out, shouting,
Woo Hoo!....What a Ride!