That's certainly true, but at least that's not going to cause an infinite loop while wandering down the structure, it's just gonna end at a leaf "ref" or "id".

In my view this is more a question of simple interface vs. simple implementation. Having cross-references at the language level gives a uniform and simplified interface at the cost of more having to develop careful tools.

Not saying refs/id are bad, but at least with a uniform syntax and language support, you don't have to reimplement custom cross-reference resolvers.