Reading up on Subaru's class action settlement for spun rod bearings provides insight into what they attempt to check for. They're denying claims for any sign of modification or abuse.
11. “Excluding Conditions” means the following vehicle conditions or modifications, which, if currently present or previously existing in the vehicle, exclude the Settlement Class Vehicle from receiving a repair under the terms of the Extended Warranty:
a. Any modifications to the Engine Control Unit (ECU) or any ECU “tune,” whether currently installed or “unmarried” (e.g., COBB Accessport, RomRaider, etc.);
b. Any “piggyback” device designed to intercept and alter ECU signals or standalone ECU (e.g., UTEC, Apexi, Megasquirt);
c. Aftermarket air-fuel controller;
d. Any device designed to increase boost from the turbocharger;
e. Manual Boost Controller;
f. Aftermarket boost control solenoid;
g. Use of aftermarket or modified mass air flow (MAF) or manifold absolute pressure (MAP) sensor (or other electrical circuits);
h. Use of wastegate pressure restrictors;
i. Aftermarket or modified turbocharger;
j. Front mounted intercooler with aftermarket hot or cold side intake piping;
k. Modification of OEM boost control system and control hoses;
l. Non-factory specification camshaft;
m. Connecting rod broken (e.g., broken from revving beyond redline);
n. Use of Nitrous Oxide injection systems;
o. Use of E85 fuel;
p. Use of alcohol injection;
q. Use of water injection;
r. Use of aftermarket fuel injectors with nonfactory specification flow rate;
s. Modification of OEM exhaust system components and emission controls, including catalytic converters;
t. Max Data well over set limits. (e.g., excessive RPMs caused by missshift);
u. Evidence of non-sanctioned drag racing and or street racing from a “stop” or a “rolling start”;
v. Evidence of any Excluding Conditions having been removed prior to arrival at retailer;
w. Multiple engine oil changes greater than 8,000 miles apart; and
x. Evidence of use in a competitive automotive event other than for static display only.
The following vehicle conditions or modifications, which, if currently present or previously existing in the vehicle, shall not alone or collectively exclude the Settlement Class Vehicle from receiving a repair under the terms of the Extended Warranty:
a. Installation of aftermarket Cat-Back exhaust (e.g., aftermarket exhaust installed after (or downstream of) the factory catalytic converter);
b. Installation of atmospheric blow-off valve;
c. Installation of aftermarket cold-air intake; and/or
d. Installation of aftermarket top-mounted intercooler.
So basically they'll try to find any reason they can to deny a warranty claim.. evidence of an ECU flash, prior modification (returning to stock), abusive driving, exceeding factory ECU parameters, etc. This implies that they review ECU logs/parameters, check for signs of mechanical tampering or abuse, and so on. This could just be a scare tactic to reduce warranty claims or they may have the ability to find such evidence..
What surprises me more is that the BOV & intake aren't excluded since they both require a tune..
The takeaway is modify at your own risk ("pay to play") since you'll be jeopardizing the powertrain warranty on your car... Just say no to warranty fraud