Of course it is
I mean think about it, is frozen *water* harder to cut then when it ain't frozen? Freezing makes stuff harder, but more brittle.
extreme example: Long time ago when they were doing antarctic exploring, they needed a way to have some minimal electricity, so they hauled down a jacobs windcharger. Because the temps there are so cold, the bearings used, made of steel, would shatter, so they made the bearings from lead, once frozen, they achieved a good enough hardness to mimic steel at normal temps. An odd engineering trick but it worked, that windcharger lasted a long time. (I know this crap from reading about all those polar explorers)
Anyway, on the wood, when I lived in maine I cut all my wood by hand with a bowsaw, you REALLY can feel the diff between hacking away in the summer and then in the winter at those nasty below zero temps, there is no doubt there at all. Running a multi horsepower smoke belcher, maybe you might wonder, but running a 1/3rd horse biodrive, you can feel the diff readily.
Conversely, I always found splitting to be a scosh easier, but ya, as long as it makes it in the first whack in, then POP. She'll either bounce, or pop, no half way there much from what I remember.