Some reading here: https://www.asic.gov.au/asic/pdflib.nsf/LookupByFileName/rg213-published-11-May-2012.pdf/$file/rg213-published-11-May-2012.pdf
Basically it is done to remove restrictions from any secondary sales of shares (including those from convertible bonds).
In Nkwe case, I assume this means that Zijin would be free to sell it's new Nkwe shares (whereas without it there might be a 12 month period of restriction). Would Zijin want to sell shares on-market to keep the price capped..? Perhaps.
All in IMO only.
NKP Price at posting:
8.5¢ Sentiment: ST Buy Disclosure: Held