This may not be the final answer, but it is their current position.
If QDX HealthID is going to give a Green status based on antibody testing then there needs to be a connection between Covid antibodies and immunity. If not, then there is increase the risks of continued transmission.
This is not the final answer. WHO said "As new evidence becomes available, WHO will update this scientific brief."
Does this mean that QMC should stop work on HealthID? No. The software could be useful for data collection and further studies. It could help collect data to determine which tests provide better results and if there is an antibody threshold that does provide a level of immunity.
When a vaccine is developed, the software could be useful for tracking who has been vaccinated.
Pointing out facts at this point that may limit the usefulness of HealthID or delay its use while addition research is done, does not mean HealthID and QMC is going to fail. It just shows that there are risks to success and people need to look at this realistically.
Blind faith in QMC is not going to get the world back to normalcy.
Per WHO:
If a solution is implemented in haste and does not properly protect the physical health of people, there is a good chance of greater widespread infections and deaths. Which is going to be more detrimental to the mental health of the world.