That would be resistance against a physical device, the comb. The only chance for lice-survival is to be full grown and still be smaller than a hair.

Yes, I agree with your first point, but there are plenty of other ways they could survive 2 weeks worth of combing. Like the eggs could be smaller than the average hair and could last longer. Or, they could go into the scalp for extended periods of time. There are ways it could happen.

The eggs (nits) are to small to comb out, that's already the case. That's why you need to repeat this for two weeks, to comb out the new lice before they start breeding.