There's (1) eGovernment platforms, where you can handle government-related business online using a login. There's (2) Digital ID cards, where you can use your phone in place of a physical ID or drivers license in real life. And then there's (3) full EU-proposed-style Digital ID, where government wants to act as a SSO provider for private online services, like social media.
Yet someone can be rightfully criticizing (3), as it would pose a major risk to online privacy, and someone else barges in with "here in [place] we have a great eGovernment platform which is very useful for filing your taxes online, I don't see why you'd oppose that". Not specifically in this thread, it's been noticeable over almost all Digital ID-related discussions in the past. Please be considerate of that.
This appears to be about (2), with the catch of it being made mandatory for anyone who wants to be employed in the UK.
For people who are already working illegally, or plan to, it would change nothing, as they could dodge any checks by sub-contracting through someone who seems to be legally employed.
The government cannot be so daft as to ignore how much illegal work happens this way, so there has to be some larger scheme at play here.