Precedence would say you are correct. And the risk calculus would agree with you, with China risking drawing the ire of the Israelis and all their “partners”.
On the other hand, the fall of the Iranian regime risks all Persian gulf nations being under the leadership of the US, and with China not wanting to be dependent on the Russians, the PLAN may want to secure its own SLOCs and Oil/gas supplies. A limited “peacekeeping mission” could see the current regime survive and de-nuclearized. Chinese involvement but not kinetically opposed to the Israelis or the US, unless those two countries push the issue.
