Nope, there's no legal obligation to carry it in the UK, although if you are asked to present it by a police officer when driving then you have 7 days to report to a police station and show it there.Whenever I read articles like this I have to remind myself of the importance of carrying your license with you in the US! I suspect you’re supposed to in the UK, but I’ve never been asked for it in 40+ years. When travelling in Europe I carry it though.
I think this will be handiest for proving entitlements, rather than worrying about handing phones to police. Does this work over the web too, like credit cards? Renew your regional railcard with the proven address on your licence. And it'd be handy for younger people to prove their age - I have to check ID for alcohol sales and the number of times I've had to refuse photographs of passports and licences... (and occasionally those trying it on by opening the Health app with bogus age information entered).