Thank you for your review.

At this prices you can get about 30-50 words article from low quality writer.

In order not to type everything again I'm just going to put a part of the coversation here and par that Copyscape sent to me as well.
I am paying for
Copyscape premium service that we all use as
industry standard when it comes to writing even with writers. It would be humanly impossible to do this (check articles) on any other level but with services such as Copyscape premium that we all rely on when it comes to writers.
These are not articles to be used on your premium sites that actually product and such, 99% of these articles are awesome filler and PBN articles and T1+ articles. For the price paid, no one can not expect manual check on each and every articles. And no one does. I just want to clear this up. If any of you guys think that I'm going by hand on each and every article for $1 a pop, this service might not be perfect fit for you.
When it comes to false positives and Copyscape premium, of course, as a heavy user I've contacted them about the issue and they provided explanation. I've accepted it and I'm happy to use them still as I see no better solution for this type of service. I am working on something extra on my own, but I'm not going to discuss it in public yet.
This is just a part of our conversation that I would like to outline here:
"
Our products rely on Google's and Bing's web indexes to locate matching content, there may be some websites containing matching content that have not yet been included in their indexes and until such time they are, they will not appear in your results, as may be the case here. On the flip side, if content has been deleted from a website, it can take some time until their automatic web-crawlers update their databases to omit the URLs or content that has been taken down, so they will still appear in your list of results."
"
... web indexes that Copyscape Premium uses when performing a search are not the same ones that are used when performing a standard Google or Bing search. In some instances there may be some differences between these indexes, which would seem to be apparent in this instance. The indexes we use also get updated at different intervals to Google's and Bing's main indexes."
So yes, they are very well aware of this situation. It happens. I must say as I said to one fellow BHWer about this matter via PM that I'm pretty happy that they (Copyscape) even provided such a detailed information and insight about how things work. This is good enough for me to keep using their premium service.