No, it's another example of the WHO telling
other people to not get ahead of themselves
because the data is incomplete.
This is the full context of the WHO's advice:
https://www.who.int/news-room/commentaries/detail/immunity-passports-in-the-context-of-covid-19
They were responding to some governments considering "immunity passports", and advising that: 'At this point in the pandemic, there is not enough evidence about the effectiveness of antibody-mediated immunity to guarantee the accuracy of an “immunity passport” or “risk-free certificate.” People who assume that they are immune to a second infection because they have received a positive test result may ignore public health advice. The use of such certificates may therefore increase the risks of continued transmission. As new evidence becomes available, WHO will update this scientific brief.'