First of all, the authors of the declarations in the example headlines are not "scientists and journalists", they are authorities and journalists. People like CDC officials or the director general of the WHO are of course scientists, but they are not speaking as scientists in those news pieces. They are speaking as politicians.
Secondly, I don't think they used the "no evidence" template so much with COVID because they were "fundamentally confused". Most of the headlines in those examples are clearly politically motivated: authorities wanted people not to panic, to keep working, and above all, to keep consuming. Hence the proliferation of "no evidence" headlines for things like the virus being airborne (inconvenient for bars, restaurants, shops, etc. - in fact one headline explicitly mentions bars and gyms); kids spreading the virus (inconvenient for parents taking their kids to school and therefore being able to work as ususal), etc. Each and every one of the headlines was very convenient to keep the wheels of "business as usual" spinning, what a coincidence, right? So no, they were not "fundamentally confused", they just were trying to bias the public towards a certain direction, and a great way to do that is to use the "no evidence" narrative which, as the post author explains, is ambiguous so no one can accuse them of outright lying.
Note that I'm not saying there aren't examples where such headlines do stem from confusion. I just don't think it's the case of the particular examples in this post.