After that claim was demonstrated to be clearly less than brilliant, the propaganda machine then began subtly (and then not so subtly) suggesting it was actually Russia that was making such claims.
But that was always plainly absurd. The last normal war Russia had was against Chechnya, another country that was tiny and practically unequipped relative to Ukraine, yet that war lasted a decade and had tens of thousands of deaths with a huge culture of great music [2] perpetually reminding people how brutal that war truly was.
You won't find a single source from a Russian political/military leader saying it'd be short, because they all knew it wouldn't be if there wasn't a quick agreement reached. The one quote people were able to find was from some television personality in some segment. But I hope Russia(ns) aren't citing e.g. Rachel Maddow to get insight into American positions on issues !
[1] - https://www.foxnews.com/politics/mark-milley-ukraine-war-pre...