This relieves the stalling symptom, but does not fix the underlying problem, which is that you have air entering the engine after the Mass Air Flow sensor (MAF) at the intake. This means the car's computer (ECU) is always having to correct the fuel added in order to maintain the proper air-to-fuel ratio (A/F) in any situation in which the manifold is in vacuum, which includes idle and cruising on the highway at constant speed / incline. If it is a minor leak, this means you're hurting your fuel economy. If it is a major leak, things get worse because the most your Subaru ECU can correct for is about 15% error in A/F. If you have more air entering at the leak than the car can correct for by adding fuel by this 15% margin, you will be running LEAN at idle, and worse, while cruising. This means there is less fuel than is needed to keep things in the cylinder from getting too hot, which can cause damage to the engine internals over the long term.
Even if the stalling goes away after the engine warms up, it is still possible you have a leak all the time but it is not enough to cause an obvious symptom (the major leak "fixes" itself into a minor leak). For my car this showed itself as a stutter while coasting down in 1st gear, like while going slowly down a long hill. I would always have to push the clutch in while trying to do this, even after the engine had been warm for many hours.
Long story short: this is a PITA to fix but the parts are cheap. Either turn a wrench or pay someone to do it for you... but you need to fix this problem if it is indeed a leak at the intake manifold gaskets. Good luck!