Violation of API RP 520 for Relief Valve

I know that API 520 states that if a block valve exists between two equipments that are supposed to be protecting against over pressure for both of these equipments by a common single relief valve, then this is not permissible until the block valve between the two equipments is removed. There can be block valves at the beginning of the first equipment and at the end of the second equipment. The question is if the block valve between the two equipments we are trying to protect is made "Car Seal Open", then is this still a violation of the recommend practice? My understanding is that it still is not permissible, but can someone verify this?