An omission really only becomes a lie of omission if somebody would feel deceived upon learning of the omission. Nobody would reasonably feel deceived by your omission of the 0.000000001% cosmic ray hypothesis.

There's a pretty stark difference. The PhD would retain their credibility if someone explained the difference between the short answer and the complete answer.

But that weather dude will lose his credibility, because his audience will feel deceived, not educated.

This exactly. After a year of high school physics and a year of mechanics and electrodynamics, they finally get around to telling you: that was kind of all lies, here’s relativity. And then a month later they do it again for quantum, and finally admit they don’t know what is really going on. But Newtonian mechanics is useful!