I don't consider the connector to be "directly buried" when it is covered with an insulation method that is suitable for the location.
I think that the only connectors that you will find to be listed as suitable for direct bury are connectors listed for grounding and bonding as these are the only connectors that would be directly buried without insulation.
Note, there are splice kits that are listed for direct bury, but the kit includes the insulation and I doubt that the actual wire connector itself is listed for direct bury.