Inconsistent format when retrieving child relationship attribute

Let's say we have a collection called Users and it has an attribute called private which has one-to-one relation with PrivateUserInfo collection.

Users collection (parent) -> private attribute -> PrivateUserInfo collection (child)

A user has read access on Users collection but not on PrivateUserInfo (child) collection. There is an inconsistency on how this child attribute (private) is returned when calling getDocument vs listDocuments on Users collections.

✅ listDocuments: private -> null

❌ getDocument: private -> []

Ideally as this is one-to-one relationship, we expect the child attribute to be either null or Map but due to this inconsistency, it results in

List<dynamic>' is not a subtype of type 'Map<String, dynamic> in type cast in Flutter.