Freedom of navigation could easily draw a military response if Iran attempted (as they've stated) to blockade oil shipments. I agree with you.
Diplomatically, Russia and China would be on the wrong side of supporting restrictions in navigation and trade. Verbal condemnation of the military retaliation at best from them.
Personally, I think Russia and China want to deescalate this situation. Economically they fare better if Iran was in a more stable situation. Neither can afford or want to be pitted against the US over Iran. The US certainly doesn't want a conflict with them. That's why whatever happens our military would be severely limited in their action. A limited engagement in Iran would also limit the effectiveness of any military actions.