Sudden map layout change and reset

So these bosses with arenas. What is up with the map layout being reset sometimes? In each case there is death or a lagout. I am guessing the instance expires and on death or lagout, it is rebuilt?

It seems weird. Like potentially bad weird. In my QA terms, I would say exploitable.

After a bit more, it looks like if you die in any map boss, it wipes the map and you just have the boss. Is this intentional, and why? It is very jarring if you find the boss, die to something, and then lose all map potential.