Obviously their concern is that these forthcoming studies will be too optimistic. They do not want healthcare workers and researchers to become complacent. They may have even had a specific soon to be released study in mind when they issued the demand.
I went back to look at it. It says they will share. It doesn’t say that they will censor or stop anything. No editor in the US would put up with that.
I think this just means they get the papers before they are published.