Don't be so sure about how much work went into those additional directives.
I worked for a UK distributor and every now and again the local CAA surveyer turned up with the latest pile of red edged bulletins and asked if any should receive AD status.
On the down side this was to the distributors benefit and not to the owners as they were forced to have the work done.
On the up side who actually knew more about the aircraft?
What was galling was when the bulletin was incorporated into the maintenance manual yet the AD remained in the additionals for no reason.