Are we supposed to syncing breathing with the pulsing? Or are we just assuming that based on similar apps for breathing?

I think the pulsation is there to help regulate the breathing. Many people take fast and shallow breaths, esp. when they are stressed out.

Because evening out the speed and taking deeper breaths help calming down with a couple of mechanisms.

It seems to me it starts off a bit too fast. But I like the rate at which it slows.

After reading James Nestor's Breath, I went through the Oxygen Advantage certification for fun. Lots of studies that show that the 4/6 or 5/5 cadence (ten second round trip, leading to six breaths a minute) strongly improves heart rate variability and engages the parasympathetic nervous system.

OP had a cool idea -- wish it hit the 5/5 cadence.