[JSeery]

When a bolt or nut is tight and you check the torque with a wrench it takes a load above it's current torque value to move it. If it moves that would indicate it was well below the desired torque value. By loosing the fastener first you eliminate the initial break free torque issue. This is a lot less of an issue with new threads and new bolts/studs/nuts with everything clean, as an engine built at the factory (I have no idea if they retorque head bolts/nuts). But a rebuild becomes a different issue and it is more difficult to get the torques to the correct values in one operation. Over the years three heat cycles have been found to be a good practice.