yes but the reason that the afr is richer is because more unburnt fuel is making it into the exhaust, that same unburnt fuel keeps combustion chamber temps to with a reasonably safe number

 

that is how i tune my car and its been fine for the 3 years i have had it. and i drive it hard. i get no knock except that random low load knock that mysteriously pops up every now and then. but under wot or part boost 0 knock. everyone has their own way of tuning and like said cars are all different this is obviously the case. i have not gone around tuning tons of cars but for the few i have tuned my strategy works the best for me.

 

tuning is knowing the best combination of safety and power to put into a car, a good tuner knows when this has been achieved...if your tuning a car for a kid that beats on it 24/7 doesnt lower boost when its cold out, and loves to be cheap and not run 93 octane then yea you better make that the safest tune you ever do cause that kid will pop his motor, if your doing ti for a person who knows what there looking at, monitors all the right information (i.e. boost,egt,afr,knock) then you can tune it a little more aggressive, in my opinion theres more ways to tune a car poorly then to tune it good, and making sure its good is a matter of patience and understanding of what exactly is going on both with the cars engine and the where the ECU looks for information....

thats just my theory...and i dont care what anyone says about it

 

Keeping the proper timing keeps combustion chamber temps more in check than running overly rich.