Ok, I think I changed my mind. My impression at this point is that Cure Dolly is wrong, because one of her core assumptions is that subject=が and every clause can only have one noun phrase (“train car”) marked by が.
From the following thread this seems wrong as adjectives like 好き can take two noun phrases both marked by が, thus having two “subjects”.
Disclaimer: I’m an absolute beginner who just likes understanding grammatical structures.
This article contains some examples and explanations of this case (among others):
I’ll be happy to be proven wrong, but at this point I don’t know how to settle this contradiction…