Interesting question. I never knew they where to norms for octane so I had to look it up. Here and most Europe use Research Octane Number (RON). They are even planning to drop 92 and offer 95 as lowest so next is 98 and 100 for modern injected cars.
Lower octane is better for stock flat heads due filling out burning in deform combustion chamber. (I'm sure this is not correct English )😂
No difference on highways, but driving around town with lowered octane, there' is more torque and engine sounds more relaxed. Difficult to explain. And yes timing is important.
Especially in my Cadillac V8 flathead, there is a significant difference.
With a compression of 4.5-7:1, who needs lead ?