Why reduce Knock Retard?

In this HP tuners worked example Andre reduces the factory knock retard table by 25%. I am curious why we wouldn't just leave it be to be as safe as possible. Is there any downside to leaving the knock retard as is? Won't it only affect the engine if we are experiencing enough knock to warrant that amount of retard?

Not sure of the specific application Andre had in mind, but knock-retard is usually a fairly coarse safety measure. IIRC, 10 degrees is common with OEM EFI systems, partly because of the variable pump fuel quality, protection for the wrong octane fuel being used, overheating, etc. Possibly more, if it can further retard the timing for knock. With a race/high performance vehicle the fuel quality, etc, should be more consistent, overheating shouldn't be problem, or other issues that may require coarse adjustment

What I suspect - I may be wrong - is that Andre's thinking is that a properly tuned engine will operate (one hopes) always outside the knock-retard trigger range, and if it is triggered it will normally be a transient condition, with a small amount of correction needed. With big retard values there will normally be a significant drop in engine torque, possibly excess EGT's etc, and by having a smaller amount, while still suppressing the knock, there will be a less significant penalty to performance, etc.

If you are logging the ECU, and when knock occurs, you may try reducing timing by a degree at a time and/ or increasing the lambda by a point so the retard isn't triggered under those conditions.

Anyone else?

In Mitsubishi tuning world it's a common practice to start tuning a new project by retarding OEM knock table. It gives you more room for safety if anything goes wrong in terms of knock - ECU will react much more aggressively in order to protect the engine from any knock level let along severe knock.