The article is a bit of clickbait, It's not so much legal fuzziness as more there's no one agreed upon international defined limit, many countries use the Karmann line as the legal standard whereas the US defines it as 50 miles. So it is legally defined It just depends on where you're standing on the surface of the planet

Should we call the limit on the where international waters start "fuzzy" just because the Chinese use a greater distance from their shores than the US and other countries?