Plague Clarification

I got curious last night and started asking around for people to spread Plague with Cassian. While only one copy of Plague would be copied (like a Damage over Time effect), no Plague was copied at all. I have spent today trying to figure out why with no clear answer. Opening up a thread on Reddit (See https://www.reddit.com/r/SWGalaxyOfHeroes/comments/78552x/plague_and_cassian/) led to answers that I had already thought through.

So..how does Plague work? Even though it is a "locked debuff", that should only affect its ability to be dispelled/cleansed. Every other locked status effect in the game (Armor Shred, Fracture, Call to Action, Backup Plan, and Bounty Hunter's Resolve) either has yellow text identifying it as a "Unique Effect" which makes it unable to be copied by Grand Master Yoda, or a specific wording in the description (Fracture) that states it cannot be copied (Armor Shred isn't a debuff and is therefore excluded from being able to be copied in any way). Plague lacks all of this. It simply seems to exist as a debuff with a locked icon, which would make it able to be copied in theory- but doesn't.

Ideally posting here can get me some clearer answers, and feel free to add opinions or thoughts on it of your own!