This was a set that was released on LEGO Ideas back in 2018. It wasn’t accepted by LEGO Ideas and so wasn’t made available for purchase. What we’re not sure is whether Mould King partnered with the designer, jjukjang, or not. Mould King and other Lego-compatible brands have been known to collaborate with real designers instead of just copying instructions online.
We really do hope that this is a real partnership with the designer. If not, then we highly encourage everyone to continue supporting the designer and their past/future designs; they’re clearly a very talented designer and we’d want to see more from them.