Medical certificates for sport events are very French... But the point is that they don't provide any medical data, they just state that the person is fine (in very general terms) performing that activity. For instance if you plan to go diving your GP will ask you a few questions and examine you then in effect write down "Sure, no problem".

Here you have a piece of information that very specifically says that persons is negative to Covid or vaccinated. Perhaps its does not say which one it is but my understanding is these are both medical piece of data anyway.

That's why I think this is very different. It's like if the only criterion for diving was being HIV negative. If a driving instructor was provided with a medical certificate that said "Sure, no problem" in that case it would be the same as getting the HIV test status of that person.

In that respect, the advantage of scanning the QR code is that there is no need to store sensitive data anywhere but within the QR code itself, which remains under the control of the individual. I think this is actually one consideration for deciding to implement the system that way.