Miller,
The issue as I understood it was indeed nearly the magnitude om my analogy; a low pressure 5-6 ksi load vs. SAAMI max. I know nothing of pressures from differning forcing cones or backboring nor have any opinion on their effect on recoil. Pattern? Yes, from my direct test experience on forcing cones alone. Backboring? I have no test experience or opinions on its effects.

What I do have the knowledge that when a firearm load accelerates a given payload to a given velocity it does so over a specific time. Change the pressure but keep velocity, payload, firearm weight, etc. the same, and a different acceleration occurs (velocity/time) of the payload. If you believe 'every action has an equal and opposite reaction' you will have to accept that the gun accelerates differently as well.

I believe some of the loads being discussed in comparison, can yield enough difference in this acceleration to be detected by people. They said so. I have no reason not to believe them. I have no data to disprove them. I do have some limited experience of shooting such loads where I believed I noted a difference.

To discount the "anecdotal" experiences of people without data to refute it, itself is to say 'only what I believe is supported by hard evidence, exists' . That approach woulda prevented pretty much any advancements in any field. An open mind to the unproven is what facilitates learning more about it.