But the PP is objectivsly correct.
By having distinct offences for rape (by penis) and SA with penetration, the UK's law has created a sentencing disparity that doesn't exist in other jurisdictions.
There disparity is plain in the sentencing guidelines. Although both carry the same maximum sentence, the starting points and the typical ranges are lower for assault by penetration. That means that acts that are broadly equivalent are sentenced differently in the UK, in a way that doesn't occur in other jurisdictions that treat penetration similarly.
That’s not a controversial opinion - it’s exactly what the Sentencing Council’s own guidelines produce.
To add - even in countries that do not make rape a gendered offence (because they don't have the by-penis requirement), where it was by-penis, that is very often relevant to aggravating factors for sentencing.
The difference is that other jurisdictions, with wider definitions of the underlying offence, tend to evaluate pregnancy risk or disease transition risk as the relevant aggravating factors, and the end result tends to be higher sentences for penile rapes but without the more vast disparity seen in the UK.
E.g., in countries without a separate penis-based offence, where a rape occurred by-penis, and the victims vagina were penetrated, there will usually be an uplift for pregnancy risk, that would not be the case for an anal or oral penetration offence.
Rape by-penis would also generally result in an aggravating factor of disease risk, which might vary as between higher risk penetrations (vaginal or anal) vs oral.
The UK is the relative outlier, because it's categorization and sentencing set-up is not based so directly on actual harm and risks, but more a general sense of the "specialness" of the penis. In that sense, it seems more like a holdover of antiquated ideas of degrees of defilement, underpinned by latent sexism.
And, as the PP has repeatedly pointed out, it is women and girls who are by far and away more likely to be victims of all sorts of sexual offence, so it is very fair to say that the UK's approach results in worse outcomes for women and girls compared to jurisdictions that view non-penile penetrations more similarly wrongful in principle, even if risk variance can justify a higher sentence.