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Is there any performance advantage here or is it just to back off the compression ratio to avoid pinging?

Thanks,
Konrad

In theory, sharp corners would provide hot-spots that would promote detonation.

In practice, I'm not sure it matters unless you have tuned your engine to the Nth degree.

--DD

Also called the Semi-Hemi, I used to do this back in the early nineties.
OK if you want to lower your CR, but I've found doing the math and shims under the barrels do a simpler and performance wise better job.

Sharp edges in iron heads are a problem as they can light off under pressure, like a glow plug.
Sharp aluminum edges turn dull when they get that hot, preventing the kind of pointed hot spots that light off.