Poster has a question:

Does this mean that Allah is ALWAYS descended, because since the Earth is round, it is ALWAYS the last 3rd of the night somewhere on Earth?

There wouldn't be any time in which He isn't descended then? It is always the last 3rd of the night somewhere or the other on Earth. And if He is ALWAYS descended, He wouldn't need to descend, but actually just stay there.

This is confusing.

Fundie has a non answer:

The brother is right, this has to do with matters of the unseen. it's tawqeefiyyah. We accept as we've heard it. But this might help a little. The concept of time, space, future, present is nothing to Allah (subhanahu wa ta'aala). Allah created time. Allah can decide to descend at once and it'll be the last third of the night in every city (no matter when that might be to us). Time is inconsequential when compared to the majesty of our Rabb. Our Creator. Please endeavour not to delve too much into matters of the unseen. it leads to destruction and kufr. May Allah forgive all our shortcomings