It doesn't say the literal opposite of it. Your quote says "British privacy rules would continue to apply to [UK government] requests for data". This is very d

It doesn't say the literal opposite of it. Your quote says "British privacy rules would continue to apply to [UK government] requests for data". This is very different from British privacy rules applying to private requests for data. Under the GDPR, and presumably British law, a private person can get a copy of your data and demand that it be deleted. According to your quote, there's no suggestion that will continue to be available. It may, or it may not, but it is not specified.