I think I may not have made my point very well.
If you write, "The boys is reading," every English teacher from Hanoi to Hoboken will mark it wrong. It is a clear violation of the subject-verb agreement rule. There is, however, no such rule governing the use of continuous-tense forms in constructions using the word while. Consider these examples:
1. Nero fiddled while Rome burned.
2. Nero was fiddling while Rome was burning.
3. Nero was fiddling while Rome burned.
4. Nero fiddled while Rome was burning.
Each of these sentences is grammatically correct and has essentially the same meaning. The choice of which sentence to use is a matter of cadence or voice and the writer's preference. I might use any of these sentences, depending on the tenor of the rest of the piece I am writing. Overall though, I always prefer to use verbs in their active form whenever possible.
I agree that while does not necessarily require the Progressive.
I read a paper while she cooked.
I was reading a paper while she was cooking.
…while the dog slept is also possible if one only states the fact.