To add a new idea to the Op:
I don’t believe everyone needs to be relaxing their shoulders. Probably depends on the individual like a lot of this stuff but I feel like I breathe easier with a certain posture. If I let my shoulders melt, it’s uncomfortable. So I keep the posture that feels right to me.
Reminds of the myth going around that when you’re catching your breath, you shouldn’t bend over with your hands on your knees. For decades coaches have been saying “stand up straight and put your hands on your head” and now current research shows the bend forward with hands on knees posture is actually effective.
Turns out that people can feel what feels better pretty easily and naturally do what’s best.
When you look up research or someone links you research, always look for the results of individuals in the study, not the whole population and not just the conclusion. If there were individual exceptions observed in the study, and you have good reason to think you’re an exception too, then you probably are.