One thing to keep in mind is that there are several oil pumps Subaru has used on various engines and all are basically interchangeable. Each of these pumps has its own spec for pressure/s, and volume at given RPMs.
Here is a cheat sheet for the volumes and pressures of the above pumps that has been posted on the web before.
To pull specs from a manual I have at hand(2008 Forester NA), here is how the specs for flow, pressure at RPM with oil at temp are stated for a 10mm pump.Oil Pump Performance(oil temp @ 176įF):- 600RPM
Discharge pressure = 14 PSI
Discharge rate = 4.9 US qt/min- 5,000RPM
Discharge pressure = 43 PSI
Discharge rate = 49.7 US qt/min
Being that the flow rates are stated at a given PSI, it would lead one to believe that they are to take into account the restriction provided by a factory speced engine build.
If this was a bench test one would expect to see the listed pressure to be close to zero or none given at all, as you can't have pressure without a restriction at the outlet. Otherwise for a corrected bench test it would likely be listed that you would need to use a specific size orifice to simulate the proper restriction of a factory speced engine.
Even with the listed 9-11GPM it wouldn't worry me as you are only going to see full oil pump out put volume at 5,000RPM+. Which is only going to be in short bursts for a Daily Driver, it at all for some.
In the case of the '08+ STI 11mm pump, another manual I have Specs it at 66.6L/min(or more) @ 56.8PSI. 17.59gal/min(or more) and calls for the same 15208AA12A as the little NAs. Seeing as Napa is doing the same and calls out the Napa Gold 7712 for the '08+ STI and the NAs with the little 10mm pump, I again don't think of the flow as being an issue.
Subaru does not spec the flow for the filter in the manual but a quick email may answer your question more then any of us on the web can speculate. SOAs customer service is pretty good about answering these types of questions.