Clarification for Pixiv Thumbnail Tagging

I received an automatically sent message regarding post #808829 and it's removal of the pixiv thumbnail tag. I thought we are suppose to not tag thumbnails with pixiv thumbnail if both the thumbnail and full size have the same resolution.

From wiki:

Do not tag images with this just because the post source has the "_s" or "_m" at the end of the filename--quite frequently, either people upload the correct full size and tack on a thumbnail URL for the source or the image is small enough that the thumbnail is the full size.

It could be a misunderstanding on my part, but I am taking the bold part as another instance to not tag a thumbnail with pixiv thumbnail.

Resolution =! filesize. Pixiv samples have different filesize, hash, and have been resampled automatically by pixiv.

Durr, I mistook filesize as the resolution of an image, not the space it takes up.

Huh. That's a little unsettling. I didn't think pixiv bothered to generate thumbnails when the resolution fit inside the limit. Well, the MD5 hashes are all that matters to me.

The sub-600h/600w ones probably don't have autosamples but it still generates one for ones of the exact dimensions because of some panic with the thumbnailer or something.