Allies take on different strategic roles depending on their strength and national conditions — that doesn’t mean China treats Iran as a proxy.
Unlike the U.S., China doesn’t force its allies to sacrifice their own national interests just to serve China’s. For instance, even with ongoing tensions with India, China has never asked Pakistan to provide unconditional military support or to block reconciliation efforts between Pakistan and India.
Pakistan has remained almost entirely independent in its dealings with both the U.S. and India — and the same goes for Russia.
That said, I do think there are some misunderstandings between Iran and China. Maybe it’s because both are ancient civilizations with thousands of years of history — sometimes we might both just be a bit too proud.