How is the proposed UK Digital ID different from EU Digital Identity already present in most European countries?

I'm originally British (and currently in the UK), we live normally in Ukraine, which ranks among the top in e-governance in the last few years. We use Diia, it has my residence permit (one of the few forms of ID that proves my right to be in the country meaning I don't need to carry a passport unless entering/exiting), tax information, driving license etc. My wife has a copy of her passport in the app and we both have a copy of our daughter's passport for ease. It's used to securely verify things and in fact has actually made it easier to get train tickets on the route we need to get home which have been routinely bought by scalpers for years who sell them for a much higher price (which on principle we refuse to pay) since verification has been brought in (train tickets are named in Ukraine and for a fixed service, this is normal). It's secure (and even in war hasn't been compromised) and isn't an issue. I'd have no issue carrying it in the UK as long as the behind the scenes architecture is similar. The UK government would probably be better off licensing the software than building their own system honestly. The concern to the idea of carrying it has, to us, been hugely overstated.