How is this not under the jurisdiction of OSHA?

Because there is a legitimate freedom of expression question here. Can you name one other example of The State (meant to mean any form of polity or government. Not state/federal) compelling speech on any other form of expression? This isn't so much as banning a dangerous practice as it is making sure viewers see condoms in use. §6720 (h) actually says

"there shall be a rebuttable presumption that any adult film without visible condoms that is distributed for commercial purposes in the State of California by any means was produced in violation of this section"

A presumption of violation if a visible condom can't been seen? It goes against one of the most important guarantees of most civil legal systems since the Roman Empire. And all for what? To force other people to do what you think they should? Compelled speech or expression is never justified. Should each actor and actress in each film produced also be required to give informed consent to one-another during the production so the audience can see that the acts are not coerced? Should they have to provide it again at the 20 minute mark to make sure they haven't changed their minds?

I'm not sure any worker is ultimately allowed to choose for themselves how much risk they will take with their lives and health

Where do you draw the line on what activities people should be permitted to engage in if you think it's too risky? Especially when it comes to forms of artistic expression and intended to influence the behavior of the audience? Should BDSM films be prohibited because there's too great a risk that one of the actors could be injured? Or because others might be inclined to perform the same acts in their own home? Should we prohibit car chases in film and television because the viewing public will be more inclined to do the same? Who are we to infringe on the agency of anyone when they have wronged no one?