Don't recall claiming it was CaCO3.
I used "Nodule" as a descriptive, not a genetic, term. I'll be more careful. However, I am used to using the term "nodular" in a non-genetic way to describe round or oblong minerals in a rock, and that is acceptable in metamorphic petrology. Which is more my field than sedimentary petrology.
Certainly this rock is not in-situ. Did it roll or fly to get here? If it were ejected, fractures would have occured at impact and at landing. More the former, I would assume.
Analogy is important - nay, it is crucial - to geologic reasoning. Sorry, that's just the way it is. It begins with the Law of Uniformitarianism. And even if it is not earth, we start with what we know and work from there.