That doesn't make sense. Winter is the best time to invade Russia because you have fresh supplies, you are prepared for winter and you have spring, summer and autumn to secure it.
The mistake is to invade Russia in late summer because the campaign will be prolonged and you will have to secure Russia in winter, with your summer clothing, which is the problem.
*edit: But don't forget about the nuclear bombs and the evilness of war itself. It's never a good idea to invade Russia.
The quote, usually known from the Princess Bride, is actually from Field Marshall Montgomery addressing the House of Lords:
The next war on land will be very different from the last one, in that we shall have to fight it in a different way. Rule 1, on page 1 of the book of war, is: "Do not march on Moscow". Various people have tried it, Napoleon and Hitler, and it is no good. That is the first rule. I do not know whether your Lordships will know Rule 2 of war. It is: "Do not go fighting with your land armies in China". It is a vast country, with no clearly defined objectives.
Montgomery didn't say except in Winter. He said don't do it all.
I’m not sure what you mean by “won”, the Japanese most certainly did not conquer Russia, which is the entire point of this old truth: that the geography and vastness of Russia makes it extremely difficult, if not impossible, to conquer. It’s a very different thing to attack Russia and have them cede territory to you, this has been done many times even by European countries.
The mistake is to invade Russia in late summer because the campaign will be prolonged and you will have to secure Russia in winter, with your summer clothing, which is the problem.
*edit: But don't forget about the nuclear bombs and the evilness of war itself. It's never a good idea to invade Russia.