I know what you are saying and thats a logical conclusion to draw.
on my X570 board, there was an 8 pin and a 4pin at the top left for the CPU, but you only really needed to connect the 8pin for normal use, the 4pin was generally only required if you were going to be putting additional demands on the VRM like in the instances of LN2/Extreme Overclocking.
I would have hoped the manual would have provided more information that just "connect one or both" perhaps a bit of bakcground as to why you might want to connect both over just the one.
I have a new GPU coming soon and am coming up short on PCIE power connections, so was looking to see where i might save one or two 🙂