Right, yes, that was early March. The guidelines evolved as more information became available and they released new advice in early April, which is far from ideal but better than a lot of governments reactions.
Their official stance before that was rigorous test, isolate, and trace, which was not done seriously anywhere outside China.
I was in China during the initial lockdown that started in late January/early February. The instructions from the government were clear from day one: stay home as much as possible, wear a mask when you go out, wash your hands when you get home, open your windows and keep your place well-ventilated. All that advice holds true today, just as it held true for SARS, MERS and other similar viruses.
I feel like the reporting from the WHO was deliberately sub-par for political reasons. For example the vacillating on masks - everyone knew that masks helped, but the WHO tried to be on the fence about it because some countries were experiencing shortages. Another example of the WHO playing politics was when they neglected to publish the advice not to trust folk remedies, since that would have gone against a Chinese government campaign to try softly promote TCM, perhaps as a form of psychological comfort to the hundreds of millions stuck in lockdown.
Living through corona has helped me to realize that successful public health policy isn't just about giving everyone the raw facts, it's also about managing people's morale and trying to influence their behavior through propaganda. I think the WHO tried to do this, but it wasn't universally successful.
There was a concerted effort from government officials,
bandwagon-joining academics (aided by journalists) in the West to downplay masking, and to ridicule and shame those who wore masks. Here is a Time article from eary March where it was described as the equivalent of “knocking on wood”. https://time.com/5794729/coronavirus-face-masks/
I am fairly certain that the US government reversed itself on masks before the WHO did (Wikipedia says WHO changed its advice in June).
Well, mask early may not have been the best choice of words then. Taiwan's reaction would qualify as early. And Taiwan is the thing that the WHO has been very conspicuously be silent about even when asked explicitly.
Their official stance before that was rigorous test, isolate, and trace, which was not done seriously anywhere outside China.