So I've experienced this for some time but testing it again yesterday, is that if you follow the Guided Breathing to the teeth, is actually causing me to slightly hyperventilate and therefore causes my stress level to go UP (because excess oxygen, decreased CO causes heart to work harder, hence HRV goes down). So I feel highly energized afterwards, not calmed. Yes I am breathing out all the way. The issue is that there is virtually no pause between the breaths, and this is where slow deep breathing works its charm, because that long pause say 5 seconds BETWEEN breathes is what signals the parasympathetic to slow down.
Maybe for athletes who have far superior control over their cardiovascular, this is fine, but for average people I think this Guided Breathing could work against its goals for relaxation. Could you get an expert to re-evaluate the timing on it. Or if you wanna get really smart, change the timings to reflect if the persons stress actually goes down.