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.