I don't know this to be true, but looking at .show in the online S3 arena just now this is what I see:
for targets scroll down a fair amount and you will see OT_88Flack 0 0 1 and OT_MG 0 0 1 . But look at structures that we know have to go down and you see OT_xxxxxxx 1 0 1 . Notice the difference, 0 0 1 for ack/mg and 1 0 1 for stuff that apparently needs to go down. 0's and 1's turn things on and off. The first 1 must mean destruction for closure is turned on for that object.
That's my somewhat educated guess.
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