JUST GIVE MY DWARF A FEW SECONDS TO WALK PAST THE WALL.
And how would Ūben know about the dangers of adamantine?
Because of hereditary tales of forts laid low before the wrath of the demons, for the sin of abusing Armok's gift.
But those tales have not existed, in-universe, in ANY version of Dwarf Fortress to date.
In general, this game sticks to DF, so we should assume it's like DF.
Anyways, surely the GM would have mentioned such apocalyptic tales?
GM's word is law, so we should trust it.
They know what adamantine is. They declare praise the miners. Thus, logically, they know about adamantine and the awful consequences it can have. Also, just because the GMs word is law doesn't mean the GM has to declare absolutely everything. Did (s)he have to say dying means you make a new char? That mining gets rid of stone? That you can make things from stone and wood?
1. They say, "Praise the miners!", indicating joy, not something like "Run for your Life!", indicating terror.
2. Did the makers of the first gas-burning stove or steam engine or diesel engine or automobile know that they were contributing to global warming? No. Just because you now one thing doesn't mean you now everything.
3. The GM doesn't need to say obvious stuff, but important, unclear stuff (if dwarves know about adamantine's inhabitants) should be mentioned.