Okay, now I buy what you say. Higher compression ratio means higher mixture temperature at the igntion point, which means greater fuel detonation resistance is required. Higher compression ratio also means higher peak combustion temperature and pressure (usually a achieved just after TDC if spark timing is set for maximum torque), but the difference is not huge.

If detonation does occur, it usually happens before peak cylinder temperature and pressure occur. Light detonation - that we sometimes can't ever hear, but is picked up be detonation sensors can occur just before or slightly after peak temperature/pressure. If an engine gets into heavy detonation, it occurs well before peak temperature and pressure, and before the piston reaches TDC.

Duke