The Eye of Flame (item id: 3075) seems to be marked by a similar collected piece, but ATT only lists one for this appearance while WoW claims this was not collected as seen in the tooltip. After some testing, it seems that this was introduced with ATT 2.5.0.

I play in Unique Mode in case it is relevant here

@ImUnicke

Huh really strange. I'm getting this as well for this Item when I refresh in Unique mode.... time to see what's being weird about it

Ah... found it.
Deadeye Monocle is the same Appearance as the Eye of Flame, but the API for shared appearances of a given appearance neglects to indicate this.

So if you have Deadeye Monocle /att sourceid:74444 collected, then this is why it's shown as collected.

HOWEVER, it appears that Deadeye Monocle is not available for Transmog! So, there's something to fix with the Unique collection logic after all since a known Source that cannot be used as Transmog should not count for Unique collection of a Source which can be used for Transmog.