I am sure you are right. Loose Cam Chain at startup until oil pressure builds.
And possible dry rod end bearings due to the placement of the filter.
Considering how many people Subaru thumbed there nose at that were complaining of excessive oil consumption, there is no way there going to say anything but this noise is normal.
If you people out there really believe Subaru gives a crap about you after the sale you need to take a good look at there history…
They screwed up AGAIN … If this noise is because the cam chain is loose until oil reaches the cam chain tensioner than they screwed up by not having a unit that keeps the chain at its last run tension. Its a ratchet device that doesn’t allow the chain to go loose once the engine is turned off. Even Harley uses oil pressure to keep there cam chains snug while the engine is running. Everyone else uses such a system also. Even motorcycles from 40 years ago with overhead cams that are chain driven use them.
But if this is dry start rattle because there is no oil in the filter and the rod end bearings are dry until the filter gets refilled… This is really bad for the motor.
Dont forget all the talk about engine wear at start up… This is like starting your engine with NO OIL until the filter gets filled.
This would be a MAJOR fkup on there part…
I would not be surprised at all if it is both.
The thing that concerns me the most is, will the chain skip a tooth once it gets older and stretches. Rattling until the oil tension-er finally removes the chain slack. That is why there needs to be a device that doesnt let the chain go loose when the engine sits…