"Usui channeled Reiki... everyone knows that don't they?."
No one knows that. We are all repeating what we were told by our Reiki Teachers and they were told the same from theirs etc. We have been told and then we Believe. Few dare to question it.
We can not know unless we experience the energy actualy (as very likely Usui did in intense meditation) and to do that is to free the mind from the always craving ego self.
Reiki is a system not the energy. At first Usui call this system Usui-do.
Reiki system imo is tought backwards. Energy channeling and energy invoking before actualy silencing the one creating the mess and wasting our energy, The Ego Self. How to fill a cup with no bottom?
There will be no true healing if we keep percieving the energy as something from the outside. Ego Self tend to separate it self from the energy via fancy ideas and fear.
Symbols are important the least. Awareness is what Reiki System is all about, developing awareness of alk that is and developing compassion but not the intelectual compassion which holds onto ideas onto thoughts onto illusion. But actualy by being present in the moment without judgement without fear.
Gokai is at the Heart of the System of Reiki.
Does energy flow better if this or that is of no importance. What is, is the awareness of our selves doubting, being uncertain, unsatisfied, needing to believe to be told ... This one is the main couse of suffering. The separated self

Do symbols get old, weak... trouble yourself not with this. Instead sit down in the morning and in the evening and observe the self which is being angry, worrying, doubting, proud, jelous, envious, and else. It is not about repeating the gokai words but actualy seeing who we are just for today.
Place your hands onto your head and calm the body just be without wishing a thing, just let it be and be aware of the mind.
Friendly Gokai