There is going to be a bunch of water (snow) trapped under the shingles and that certainly is not good for the osb sheeting when it melts.
I realize it's not code there but my God man they need to use some felt.
If they insulate before it warms up all that melt water is going to drain into your new insulation.
The melt water is going to get all over your new electrical also, drywall, etc.
It will be fine...