Think about it twice, please.

Please read the original post again. Seems the situation he is in is not what you said. The conclusion you made is just based on your assumption.

A possibility:

His parents got 6 months multi-entries B2 visa in US consulate in China, but only got 3 months, or 2 months, even only 1 month permission of stay on their I-94. Then, they applied status extension and already got approved. So, right now, after 3/2/1 month(s), they have valid/un-expired multi-entries visa and extended stay status simultaneously. ---- Base on my own understanding, under this circumstance, my conclusion is YES, to his question. Still, I could be wrong.