While this is true, the pronunciations are not consistent across languages that use Devanagari script. ज्ञ is pronounced like "gy" in Hindi, but "ny" in Marathi. ज is pronounced like "jy"(with the य sound) in Hindi-ish languages, but without य in Marathi. Some sounds are completely missing/unused is some languages, like ळ and ण.

So non-native speakers with another Devanagari language as mothertongue still get pronunciations wrong.