The "cliffhanging" is something easily doable in any ages in Gehn shard. The only thing you need for that is a collision wall not at 90 degrees or higher angle.
It's the benefit of Hoikas' mods on the physX engine

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In MOULa, I wouldn't expect those mods to appear. I don't think Cyan would like the fact that we would all being able to do "cliffhanging" everywhere!
Since MOULa reopening, Cyan didn't stop any skydiving activities in the Cavern and we have a total freedom of doing whatever we want there. It's still a marginal activity done by let say less than 5% of the Caverners.
Go visit...TOC's COD on a busy day

the "skydiving afficionados" is around 75%. Why? Because it's easy to go everywhere.
In Gehn, visit the public Ae'gura, you will see many explorers climbing collisions everywhere more than in MOULa's public Ae'gura!
So...yes you can do "cliffhanging" in Gira in Gehn, but also in every ages on this shard but this isn't reproducible in MOULa.