According to the web page, New Gulim includes all of CJK, for Koreans this means Hanja, which are thousands of Chinese characters that haven't really been used to write Korean since the 19th century.

The actual Hangul (Korean syllabary) characters require about 30 consonants/clusters and 21 vowels/dipthongs which can appear in characters in 9 different layouts. It's much more work than the 26 latin characters, but most of the font design is going to be copy/paste.

So you could say the purpose of New Gulim is not to create a "Korean font" in the sense that a font you can write Korean with, but rather the sense that Koreans can use it to write Korean mixed with Latin, Chinese, Japanese, Cyrillic, and Greek characters with a unified design between scripts. That's a tall order.