It's not. pineeal glands produce melatonin, the hormone that controls sleep.
The pineal gland is significant to occultists because it is the only part of the brain that is singular. You only have one. Every other part is part of a mirrored bilateral set. Thus they speculate that this is the seat of the soul.
It is a common blackhat technique to throw us off whenever we get close to something is by injecting a little bit of disinformation. The best lie is one that is as close to the truth as possible. The factoid about adreanochrome being injected by eating brain bits is some of that. It wouldn't surprise me if they do eat this gland as some sort of ritual to absorb the soul of some poor person. And I suspect that consume the blood of their victims after causing them to die during a massive adrenaline surge, which then oxidizes and has a narcotic effect. But connecting the two concepts makes no sense biologically.