Great illustration of why high foc was not a thing way back in the day. Tuning was and is to get as close to perfect arrow flight as possible with the chosen components. With a glue on head and wood arrows there werent and arent a ton of choices. The chosen head is going to dictate the spine required for good arrow flight. The required spine is going to, within a range, determine the weight per inch of the wood shaft and thus the total weight per pound of draw. Those limitations made high FOC almost an impossibility. That is largely, not solely, where the recommendation to shoot 10-12 grains per pound stems from. Terminal penetration was enhanced by the arrow getting to straight flight as quickly as possible and hitting the target flying straight. If the arrow needs more flight correction it is using energy that could otherwise go towards penetration and as everyone is aware square impact to the target will yield greater penetration than off square.
A bow produces a fixed amount of energy for every shooter. Every arrow has a certain amount of energy it can accept and fly right. That is why I have always started every build with the head and build from there regardless of the shaft material. With carbon there are way more choices that can be made to work but that can certainly come with a lot of chasing your tail. Pick your head, build an arrow that falls in that 10-12 gpp range and make sure it is flying as perfectly straight as you can get it and go kill stuff.