Instance expression without choice filter returns first value only when used in nodeset context

[lognaturel]

Forum post: https://forum.getodk.org/t/collect-choice-filter-using-instance-requires-additional-term-to-function/49518

join(' ',instance('submissions')/root/item/state) is expected to return all states joined together but only returns the first state.

These expressions have the expected behavior:

• join(' ',instance('submissions')/root/item[country=${country}]/state
• join(' ',instance('submissions')/root/item[name!='']/state