I noticed all circular saw blades have a diamond pattern around the hole in the middle. I am guessing this is to prevent warpage as it heats up or is there some kind of saw that uses a shaft of that shape?

Yeah, I know my hand tools, but this one i wasnt too sure about

old power saws had a matching diamond arbor to clinch the blade while in rotation, later its been determined that compression by heavy washer and bolt would work.
good luck.

Skill worm drive saws used the diamond.