You're missing the point, the word "unlock" is used in most of the references to this feature posted here meaning, to me, the solenoid is energized only for unlock.

We both agree that the solenoid valve opens to vent the circuit and unlock the converter but the disagreement is whether the solenoid is energized to close the valve and lock the converter or whether it's energized to open the valve and unlock the converter. I see no absolute proof of either here.

Perhaps I'm too pragmatic but it seems to make more sense to energize the solenoid for a short period of time to part-throttle unlock the converter rather than to have it energized the whole time the converter is locked up.

As noted earlier, before the solenoid valve, the converter locked and unlocked hydraulically based on road speed/throttle only...it would unlock under some heavy throttle activity or when the car slowed enough for it to shift out of third and shut off the fluid source to the converter lockup circuit . To my way of thinking, the solenoid valve was installed to make the unlock at speed more controllable to answer driver complaints that forced unlock wasn't consistent when based solely on road speed/throttle pressure.