Saved object export format for Searches

For Kibana 6.6, I have exported saved objects from Kibana for offline analysis of broken dependencies.

I'm trying to understand the relevancy of index pattern ids per filter and how it is that they can be different from the index pattern id for the overall saved search.

Are the per filter index pattern ids relevant in terms of breaking execution if the dependency is unresolvable? Can anyone please clarify this export format?

_source.kibanaSavedObjectMeta.searchSourceJSON:

{
    "index": "index-pattern-id-1",
    ...
    "filter": [{
        "meta": {
            "index": "index-pattern-id-2"
...