Here's what I remember from my technician training at Toyota regional headquarters many many years ago.
When the fuel air mixture ignites in the cylinder it is a controlled burn and not an explosion which would be an uncontrolled burn. The engineers through testing know just how long the flame front takes to cross the combustion chamber and burn the air fuel mixture.
If you take an engine designed for regular 87 octane fuel and increase the compression through say head work or excessive carbon build up, the flame front speed increases and you can get detonation (pinging/explosion)
Higher octane fuel burns slower than lower octane fuel. By adding a higher octane fuel you slow down the flame front and stop the pinging/damage.
So along that line. If you take a good condition engine that is engineered for 87 octane fuel and just introduce premium fuel you slow the flame front and decrease power. In reality you will probably never know the power is reduced without laboratory equipment, but you have still effectively lowered the power output of the engine.
on the flip side, higher performance engines typically have higher compression ratios and need the higher octane fuel to slow the flame front and prevent detonation.
