To clarify this; women in the UK can commit this offence as an accomplice, and anyone can potentially be convicted of the equivalent offence Assault by penetration ie. 'rape' with not a penis objects.
If you detach and consider "the Law" as a standards document it makes more sense to read the two as "old school rape" definition being grandfathered and replaced by the newer Assault by penetration and realising that there's still a whole other spectrum of sexual assault behaviours that can be considered under law that don't involve penetration.
Like mathematics, engineering, and any number of other technical domains, Law is riddled with precise domain definitions of words that don't always align with common non technical understandings and casual usage.
