A part complete QR code not passing muster for the travel and domestic element of personal usage is my concern as well . As the way things are going , it looks like showing a fully up to date QR code , ie showing 1st /2nd AND booster vaccines detail is potentially going to be a requirement , not just a maybe need to have .Well, that's more than I can see. But I doubt that will pass muster for the travel pass side of things will it. As others have said - No bar codes.
Faffing around on the NHS app hoping to obtain evidence for either border pass through or gaining entrance to whatever place , is not going to endear anyone to said border post personnel or door keepers at any establishment .
I am not a software or app developer , but can it really be so difficult to have a fully national and common to all methodolgy of recording ALL vaccine info on a QR code , ready to show when requested or required ?