An opaque white layer is printed underneath portions of Pokemon cards that the artist would not like the holo to obscure. Cosmog has this opaque white layer, which is why the holo does not bleed through on it.
In the error copy, it appears that the other portions of the card (i.e., Lillie and the background) were not given this opaque white layer, but Cosmog had received it. Sometimes this is categorized as an “Insufficient Ink Error,” though I personally think that it should be called an “Opaque Layer Error.”
This is called a Pinched Layer error.
Hope this helps!