regproc and when to schema-qualify

I was idly following along in GSoC 2017: Foreign Key Arrays
when I noticed this:

=# select * from pg_amproc where amprocfamily = 2745;
amprocfamily | amproclefttype | amprocrighttype | amprocnum |
amproc
--------------+----------------+-----------------+-----------+
2745 | 2277 | 2277 | 2 |
pg_catalog.ginarrayextract
2745 | 2277 | 2277 | 3 |
ginqueryarrayextract
...

where only ginarrayextract is schema-qualified. It seems to be
regproc's output procedure doing it:

=# select 2743::regproc, 2774::regproc;
regproc | regproc
----------------------------+----------------------
pg_catalog.ginarrayextract | ginqueryarrayextract

The manual says regproc "will display schema-qualified names on output
if the object would not be found in the current search path without
being qualified."

Is regproc displaying the schema in this case because there are two
overloaded flavors of ginarrayextract, though both are in pg_catalog?
Could it be searching for the object by name, ignoring the argument
signature, and just detecting that it hit one with a different OID first?

-Chap