The macrons are for length, not stress. Normal stress in Imperial Sinemi is root-final. The repetition of the same notes is supposed to be for the purpose of entering an altered state. Kind of a meditative thing? It's not uncommon to hear a Sinemi humming the tune while focused on some task. It's also used to calm oneself down. Having a common cultural practice for such is very useful in a world where heightened emotions can rip open holes in the fabric of reality, letting loose the wild energies of the spirit world.

(Also, most of Simemi cultural effort is spent on fancy hats )