I don’t qualify but I’ve just had a look and it seems pretty straightforward. No catches that I can see.
I think the idea is they want you to build up a bit of an emergency fund so if you can save maybe £2 a week -which on UC is no mean feat – they will add an extra £1.
If you have a few pounds spare, that’s a better regular return than anywhere else I know of. Good for school uniforms. Or the cooker breaking. 🙂