What is the purpose of the diamond knockout on a circular saw blade?

Some heavy duty framing circular saws, mostly worm drives like the DEWALT DWS535 have an inner arbor washer specially shaped to take a diamond shape to reduce the possibility of the blade slipping while cutting through wet, or plain tough material like roofing…
Something to remember is, the direction the blade spins is the direction that keeps the blade tight even as they bog down. The more it bogs, the tighter the nut can become making it really difficult to loosen the nut when you need to change blades. And the more powerful the saw like on a worm drive, the tighter that nut becomes…  Enter this diamond which helps spin the blade, without that over tightening of the nut you may have with a regular round arbor…
Here is a picture of the inner arbor washer on the DWS535 and the DW3192 blade that is on it… See the diamond shape on the washer and the diamond knockout of the blade?
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