There's only two ways one could have been contradicting information from the WHO which was later revised prior to them revising it. Either:

1. They really did have some insight or insider knowledge which the WHO missed and they spoke out in contradiction of officialdom in a nuanced and coherent way that we can all judge for ourselves.

2. They in fact had no idea what they were talking about at the time, still don't, and lucked into some of it being correct later on.

I refer to Harry Frankfurt's famous essay "On Bullshit". His thesis is that bullshit is neither a lie nor the truth but something different. Its an indifference to the factuality of ones statements altogether. A bullshit statement is one that is designed to "sound right" for the context it is used, but is actually just "the right thing to say" to convince people and/or win something irrespective of if it is true or false.

A bullshit statement is more dangerous than a lie, because the truth coming to light doesn't always expose a bullshitter the way it always exposes a lie. A lie is always false in some way, but bullshit is uncorrelated with truth and can often turn out right. Indeed a bullshitter can get a lucky streak and persist a very long time before anyone notices they are just acting confident about things they don't actually know.

So in response.

It is still a good idea to censor the people in category two. Even if the hypothetical person in your example turned out to get something right that the WHO initially got wrong, they were still spreading false information in the sense that they didn't actually know the WHO was wrong at the time when they said it. They were bullshitting. Having a bunch of people spreading a message of "the opposite of what public health officials tell you" is still dangerous and bad, even if sometimes in retrospect that advice turns out good.

People in category one were few and far between and rarely if ever censored.