For some reason, this piece is only allowing you to use finishing reagents if you’re specialized in Sculpted Armor, despite it being in the Large Plate Armor tree. Not sure if this is affecting the skill points as well, but something to check out.
EDIT: This morning I did a follow-up and the Dredger’s Plate Breastplate must be pulling stats from the wrong tree as well. I am currently specialized into both the Breastplates and Greaves full 25/25, with 30/30 in Large Plate Armor, and 30/30 in Armorsmithing. This should mean I have the same Skill for both the Legplates and the Breastplate, but the Legplates are showing as 343 Skill, while the Breastplate shows as 203 Skill.
EDIT 2: I checked with another crafter on our server and they said Sculpted Armor is what you need to craft chests, which makes no sense, since it’s in a completely different tree (Large Plate Armor).