No, it's much worse than you suggest. Quoting the government:
> The government therefore wants Apple and Google to block nudity across the whole device by default, so they can only be deactivated via age assurance.
All smartphones and tablets will be required to detect and block adult content on the device. You can avoid it by showing photo ID, but it's bizarre that the default state should be to assume the user is not an adult until proven otherwise.
Article 1 of the ECHR guarantees that "every natural or legal person is entitled to the peaceful enjoyment of his possessions". "Until they show government ID" isn't in there!
Perhaps I'm jumping the gun to assume this will be used as a precedent to require on-device scanning for illegal content, and further extended from smartphones to desktop PCs. However, I'm not optimistic.