This isn't quite it. They've mandated that any website offering content unsuitable for kids (for the most part, this means porn websites) has to have age verification in place. This has to be more than just the old-school "are you over 18? yes" checkboxes that sites have had for years. In general, it means submitting your ID to some random "age verification provider", who does god only knows what with your personal data.
Mostly, it's adults trying to access legal adult content who have been impacted by having to send ID to unknown, often foreign, companies, and it will not stop a single teenage boy from loading up porn.
Some issues have come from trying to tell non-UK-based websites what to do. I think the plan is to block those websites. Personally, I think it'll simply funnel users who would previously have stayed on legal adult websites onto the shadier corners of the internet while harming content creators' incomes through increased use of pirate material.