I think the same is true for channels too but I’m not near a computer to check.
I’ve abused the v1 API heavily* and haven’t found anything it couldn’t marshal. Though I’m yet to apply the same “fuzzing” (for lack of a better term) to v2.
* the v1 JSON marshaller underpins some core functionality in my alternative $SHELL. So I’ve thrown a lot of exotic type structures (by Gos standards at least) at it.