[Arknights] What is the source of this pool description

I was looking through the Arknights 3rd Anniversary illustration pool because I noticed the posts there are more suitable for official art instead of guest art. Then I noticed this line while editing the pool description:

The last 3 post #5322574, post #5308234, post #5325710 are drawn by artists who are not officially invited.

I didn't bothered a few years ago but looking at it now, what is the source of this information? First of all, fanart shouldn't be put in a pool of official celebratory illustrations. And according to the collection on NGA, post #5308234 is official?

The first post #5314379 is official art for the 3rd Anniversary.
The last 3 post #5322574, post #5308234, post #5325710 are drawn by artists who are not officially invited.
The rest are drawn by official invited artists.

This version was written by @KeH

magcolo said:

I was looking through the Arknights 3rd Anniversary illustration pool because I noticed the posts there are more suitable for official art instead of guest art. Then I noticed this line while editing the pool description:

I didn't bothered a few years ago but looking at it now, what is the source of this information? First of all, fanart shouldn't be put in a pool of official celebratory illustrations. And according to the collection on NGA, post #5308234 is official?

This version was written by @KeH

The source of the information is the artist’s own Weibo. It seems that the artist invited by the official will post a forwarding lottery post on his or her Weibo.

By the way, post #5308234 is not official art.

Then the ones that are not official should be removed from the pool.