Well Im a tech at a Subaru Dealer..... I know this for FACT. There is no "black Flag" policy. That doesnt exist, however if you had some previous work done that the car needed to be called in to the tech line for some kind of assistance. Then and only then do they ask if the car is modified. So, I call B.S on the tech. He just wants the job as "customer pay" because warranty is only going to pay him 10.4 hours of labor. Where as customer pay is 16.5 hours labor. The compression test and leak down test should be covered under warranty. Thats how it works, if they find that the cause was from modifications then they will deny a claim for parts warranty. Subaru gives you the benefit of the doubt that the engine that went into your car may have had a failure that WAS caused by a failure on their end. If it turns out its from abuse or because you tuned it they have the right to say, sorry not gonna happen. BUT they still should cover the compression and leak down test as it is for them to determine a cause. If they didnt get written or telephone consent from you for more things or more diag you can tell them to eat it and you are coming to get your car. By law they have to have that, all phones there should be recorded.
Now, where can you go from here. This is what I recommend! Call the service Manager for the dealer. DEMAND that the Subaru Field Service Rep call you so you can explain the situation to him and what you believe should ultimately be done about it and what is fair. In most cases there will be a 1 time exception and it will be covered. If not try to get them to pay the labor and you pay parts, or vise virsa. Happens all the time when an actual cause cant accurately be 100% be determined.
This is what I hate about my job, when other techs dont give the customer the benefit of the doubt and just shoot for the customer pay route. Yes the car was tuned, but for what? Just minor fueling....... lets hope so.