It's either ignorance or cover-up.
There's no way we could know for sure if a virus is made in lab, unless whoever was making it kept a detailed record of every step and process and publicly acknowledge it.
But the problem is, while we cannot confirm that a virus is man-made if the maker(s) were silenced or denies it outrightly and all evidences have been destroyed, we cannot confirm that it was not man-made either.
That's why it doesn't sound right when W.H.O declares with high confidence that SARS-CoV-2 was not made in lab, because there simply isn't enough evidences to support either side of the claim. The WHO investigations were like police carrying out a breathalyzer test on someone to determine if he/she was drunk-driving one year ago, it's just illogical.
The evidences available at the moment do not support either claims strongly, and W.H.O's official statement that SARS-CoV-2 is highly unlikely to have originated in laboratory is not backed up with evidences.