Spiky

Only for USA-based car companies is that true. When all 3 of them nearly disappeared around 2000, they finally realized that maybe reliability was something consumers wanted. I wouldn't say "early 80s", either. 90s they were still mostly junk. The trucks may be an exception.

DNA Dan

The bleed down happens in the phasers themselves. I don't think there's any maintained pressure here. The oil is simply resting inside the phaser. I can see an exit hole on the center of the phaser where I assume the oil spins out of when the engine is running. Depending upon which way this hole is sitting when the engine shuts off might determine if the bleed down happens or not. When I first noticed mine, it was intermittent. Even on a long cold soak, sometimes it would do it, sometimes not. Once you've rattled and dammaged the phasers enough, they bleed down all the time, then the chain gets stretched from the jerking at startup, then the guides start busting from the chain slap, then you start wearing the front cover case or potentially jump a few gears on the chain.

The phasers have a new part number so they must have gone through a revision update from when the trucks were first manufactured. Actually, a lot of the parts involved have gone through revision updates.