So: where did it come from? Who decided that 'Russia's full-scale military invasion of Ukraine' was the thing to say? Who communicated to everyone in the media that this was now the 'proper term', even though it is wrong and misleading?
It's like that thing we saw a little more recently: one particular morning the news was full of references to 'small boats'. Small boats this; small boats that; stop the small boats; etc. Everyone started the same day. Who told them? And why was their being told -- dictated to, in fact -- not a news story? Because by rights it is.
M.