From my understanding, the premise of revolutionary defeatism involves supporting the defeat of your own bourgeois government. I am an American. I am perfectly fine with that when it comes to things like US military actions in the Middle East. However, there has been one enemy the United States has had that is definitely quite different, Nazi Germany. It's pretty much universally believed among the left that Nazi Germany was bad and should never be supported (and that's for a GOOD reason).
But how does revolutionary defeatism square in with something like that?
I need to read more to talk authoritatively on the issue, but I'm pretty sure this is the exact kind of thing Mao was getting into when he spoke about primary and secondary contradictions. Even though the ultimate goal is to dismantle capitalism, driving out Imperial Japan was a higher priority in the short term than defeating China's domestic bourgeoisie. So yeah, there are counterexamples to Lenin's line during the Bolshevik revolution.
One point all these theorists hammer on is the need for practice to reflect the conditions. We can't just reenact 1917 like a cargo cult.
It’s about hierarchy of needs and planning.
Defeatism is only a good idea if the winner would push things forward towards goals.