In practice enhanced disclosures would show this up.
The police would have to have a very good reason for not disclosing this.
Plus any employer could just google his name.
So the public should still be protected.
When perpetrators get put on the SOR it isn’t for life it’s only for a set time, usually not more than 10 years so it’s not really a very good tool for protecting the public.
I hope the family do pursue a civil case but with him being a student he probably has few assets to pay out compensation so unlikely they would get anything/much.
There is criminal injury compensation and I’d hope she’d get that.
As for unis having sex offenders. Given that they usually have 15000+ students it’s highly likely that there are sex offenders at every uni in the U.K.
There are no disclosure checks done on people moving into halls of residence.