Hello Tom,
this is somewhat similar to what happens with origin code.
the network command provides routes with an origin code of i internal
redistributed routes provide an origin code of ?.
Aggregate-address origine code depends from configuration and from codes of component routes.
Going back to your question:
Both redistributing and using aggregate-address creates locally originated routes but with some loss of details.
for aggregate-address the original AS path of each single component route is lost so it is information that lacks some information in comparison to original data structures.
This may explain also the hierarchy in locally generated routes.
To be noted that first two neigh default-originate and default-information originate comes into play only when it is the case of deciding what default route to pick up to send to a neighbor:
first command neigh .. default-originate wins for being more specific then second
default-information originate should win over using network 0.0.0.0 (that is a possible way to generate a BGP default route if a default route exists in the local node IP routing table).
Hope to help
Giuseppe