I see you have confined your question to the justice system. Does that mean you agree its not considered the same in society? Because the two are connected.
No, I think the first thing to understand is whether the different categories have different outcomes. Does using different words actually make a difference. Is rape actually taken more seriously? It is actually unequal?
The four categories of sexual offences are gender-neutral when it comes to the victims. The only gender-specific offence is rape, when it comes to the perpetrator.
So why not call it the same under the law? Because if you have been affected by this, IT DOES MAKE A DIFFERENCE.
I can understand this. But a change in the legal definitions to broaden 'rape' to encompass section 2 and qualifying section 4 offences does require thinking about whether it would have an impact, and whether there is evidence that rape is actually taken more seriously.
I can see how this is really important to you, and I get that, and that it feels to you that the word 'rape' is taken more seriously. That's not necessarily my experience, and the high-level stats I've seen don't really back it up, which is why I'm asking if there's a better evidence base.
Laws don't get changed without an evidence base, particularly when there would be no change in outcome. So it's a question of whether there's evidence to change the law - or whether efforts would be better spent at raising awareness and acceptance at the idea of male victims and female perpetrators of other classes of sexual offences, as we are starting (very slowly) to gain acceptance of the idea that a victim doesn't need to fight back, or for there to be physics violece, for a sexual offence to have occurred.