HEY - is this vehicle still qualified for Subaru's extended head gasket replacement campaign - that's up to 100,000 miles on some 2000-2002 EJ25's...sounds like his may be???
Just for giggles you might want to check the backside of your engine assembly. The external leaks like your 2001 have are very obvious but do not necessarily cause puddles on the ground. They actually leak very slow at the rear of the engine and run down the back of the engine. It can run down the engine, motor mounts, cross member and burn off before really hitting the ground.
My guess is the old stuff is ignition related and the newest stuff is a different problem - loss of coolant was an external leak that was slow and went unnoticed until the coolant level dropped too much. hard to say over the internet without seeing anything, but based on EJ's and 2001...and what i'm reading i think that's the most likely scenario .
Your 2001 is a candidate for the Subaru coolant additive, it should have had the coolant additive added to it (that is for 2000 - 2002 EJ25's, not earlier ones).
As far as I understand it's for external leaks ONLY. I'll get with the mechanic today and have him double check...