undocumented gallons treachery puzzle

This is an undocumented gallons treachery puzzle not mentioned in the quest guide that I managed to figure out a few years ago when I used a noclip cheat to walk into the fire room without fire chasing me.
The first switch opens the fence around the second switch, the second switch opens the fence around the third switch, and the third switch makes the rock explode revealing a hidden box.
The box was always empty in my experiments but it was always the secondary box variant which I believe can probably have different drops than the common boxes. I really would like to know what would happen if someone would solve it under normal gameplay while running from the fire.
I think it may be possible to solve the puzzle under normal gameplay without any cheats with a well coordinated team so I'm very interested to see what happens if someone does that.
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