I'm in two minds about this one. Consenting adults who do it safely etc then I guess like anything that's up to them. On the other hand, you don't want teenaged boys seeing it and thinking it's normal either.
However, this is where it all goes to shit:
The original part of the Online Safety Act was meant to prevent kids from accessing porn in the first place. Adding additional legislation just proves that all it did was teach kids how to use VPNs. Lets be honest, parents were putting measures in place to prevent their kids accessing porn, usually at an ISP/Router level. Teenagers are smart as fuck though and had already found a way around that so when the government came along with their policy, they were already set up to circumvent it.
And putting it at the same level as Terrorism and Sexual Abuse? That seems heavy handed to be fair. Both of those things are terrible and should be illegal but given that they are still prevalent, it's safe to say that legislation is not as effective as they would perhaps hope it would be.