What they mean, and to take an example that it purposely extreme: If you kill someone in a country you cannot avoid accountability in law by fleeing that country.
If they breached laws and regulations then withdrawing their service from the country afterwards does not change anything regarding those breaches (investigation still ongoing, though).
It's not comparable because the "crime" has been committed in the hosting country (where it's arguably not even a crime) and it's a bad example because there are many incidents of murderers fleeing to non-extradition countries.
I did say it was extreme on purpose to make the point clear, or so I thought. Looks like it isn't clear to you...
Whatever you think of my example, it is exactly the same legal reasoning at play here. If you broke the law then withdrawing does not change that and accountability.
> It's not comparable because the "crime" has been committed in the hosting country
Obviously not, that's the whole point: They may (investigation ongoing) have breached UK law. So, to really labour the point, if you breach the law in one country then cutting links with that country afterwards does not change anything.
Now, to be a bit more substantive than this tedious bike-shedding, I think the UK are just trying to send a message here even if enforcement may be difficult. The EU could do the same with the GDPR since it is the same type of law (global reach and applicability).
I genuinely think your example is bad and the legal reasoning is bad. A better comparison would be AM Radio broadcasting something obscene into the UK from let's say belgium.
If they breached laws and regulations then withdrawing their service from the country afterwards does not change anything regarding those breaches (investigation still ongoing, though).