Based on the previous thread about dusk leathers, it’s possible the screenshot is fake. The OP in the other thread made a new comment about it recently.
Two people from the other thread also posted their results, in which out of 20 successful desynths, there wasn’t a single dusk leather. A friend of mine also didn’t get any out of 6 successful desynths. From the cat became hungry site, there are currently 17 results posted and none of them are leathers. The two people from the other thread may have posted on the site, so these 17 results could be repeats though.
I would wait a bit until someone else gets a leather from this fish before investing a lot of time into it.