You mention "draft" and this puzzles me because the paper is not marked up as a draft and SSRN is specifically an open access repository for working papers, not drafts.
I've sent many documents to people that weren't marked as drafts. Simply saying it's a draft seems to be enough for most people. And it is not uncommon at all for people to post drafts on SSRN.
As to the allegation of plagiarism...
It is well known that multiple versions of this document were shown to various people around that time (July 2017). Some were word documents some were PDFs. It was in fact being very actively worked on not only by CSW but also by other nChain staff as well as versions being sent to a 3rd party editing company
Editage. Many versions of the document contain comments about intended later edits. Including:
Please be sure to update this number once all changes are finalized.
The typo in this citation will be resolved once the citation format is corrected (changed to Vancouver style).
Now the following point is important because CSW's has been characterized as willfully attempting to plagiarize the work of Liu & Wang.
The following citation was actually present in some of the earlier versions of the document.
This analysis relies heavily on a matching of a Roulette strategy that is analogous to the Selfish mining strategy. This strategy was propounded by Wen Liu & Jinting Wang in “A strong limit theorem on gambling systems” (2003)
At some point a version was created that was missing the citation. I don't know how but the most obvious explanation is that a later version branched off one that was made before the citation was added. Given the amount of activity that was going on at the time with the document with multiple parties involved it is not hard to see how this could happen. Document version control is an administrative function that sometimes goes awry.
I do think it would have been better if the acknowledgement had been in the text of the paper rather than the intended footnote. However,
this makes it clear that CSW's intent was make it known that his work relied heavily upon the Liu & Wang paper, borrowing from it to make his point with some adjustments. It is not uncommon for people build on the work of another, and say it summarizes things well, and make slight twists to make a point.
A PDF version of the document can be found here:
http://s000.tinyupload.com/?file_id=00729637117461182342
A Word version of the document can be found here:
http://s000.tinyupload.com/?file_id=07377534997138073836
It will be noted that file modification date on the word document metadata is dated a couple of days ago, this is because the original version was password protected and saving the unlocked version resets this date. I have made a screencast of opening the locked version of the file, showing the modification date, saving an unlocked version and uploading it to the link above.
I recommend turning on subtitles to help understand what is going on. I will leave the video up for a few days.