There are several pauldron/shoulder armor accessories that do not have an attachment part, such as the one seen below.
ex: Archfiend’s Trophy Shoulders
Due to this, they appear to default and instead follow the head.
Inclined to believe this isn’t intentional, as this can be seen not happening on the majority of the pauldrons on the platform.
The one above is using “LeftCollarAttachment”, though many other pauldrons also use “NeckAttachment” or “BodyFrontAttachment”.
When viewed in explorer, you can clearly see they do not have any attachment added to them.
(It also appears to be classified as a “Hat” instead of an Accessory)
List of effected accessories
Archfiend’s Trophy Shoulders
Overseer Armor Pauldrons
Lightning Cobalt Pauldrons
Korblox Shoulder Pauldrons
Cobolt Lightning Pauldrons
Magmawrath Pauldrons
Redcliff Elite Knight Pauldrons
Winged Pauldrons of Achievement
Ninja Shoulder Armor
Ultimate Competition Armor
Armor of the Last Goodbye