IIRC, adventure mode will be the mode where you can't mine everything in sight, kind of like the opposite of creative. So there is an important difference in calling this the adventure update, where there'll just be more of a reason to explore beyond the nearest branch mine, versus the adventure mode where I believe the point is that if you get lost, you can't just start breaking down walls (or if you can, it'll be at a significant cost)
Personally, I wish it if the hatches just disappeared when they activated, then reappeared. Visually make it look like it's going 'into' whichever solid block the trap door is next to (and obviously when it's unactivated, come 'out' of said block)
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