Im not sure Phonetically  is usually a labialized postalveolar approximant  The labialization could cause vowel changes like the development of a labialized velar approximant at the end of the diphthong Though its odd because theres an unrounded vowel directly after the vowel in  which would maybe not usually be rounded I guess the reason why would depend on the precise phonetic change Im not quite sure what it is the change of  from nucleus to edge of the syllable from full vowel to semivowel the change of nearclose  to close  or the development of final  Hard question