[2020] Harmonious resonance activating with no crystal armor

As it says in the title, I am currently wearing nothing but a crystal hatchet and enhanced excalibur, yet every minute or so I get the chat message "Your crystal armour resonates with the power of Seren" and my prayer drain stops. I am using superheat form while woodcutting acadia trees. Unless I am unable to find it on the wiki/reddit, the only way that seems to be able to trigger is by owning the full crystal set as it says here. Is this a bug? Or is there some other reasons that it continues to trigger even though I own no crystal armor at all?

Thanks!