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■ Plurals in speech: the alternation between /ɪz/, /s/, and /z/

[1] i /ɪz/ after the sibilants /s/, /z/, /ʃ/, /ʒ/, /ʧ/, and /ʤ/

ii /s/after other voiceless consonants

iii /z/ after other voiced sounds (including all vowels)

Extract from The Cambridge Grammar of the English Language/Rodney Huddleston, Geoffrey K. Pullum

Page - 1585

George Galloway MP at 0:15 pronounced the sibilant suffix in the word difference(s) here as /Is/ while below it is /ɪz/.

It looks queer to me. But since I have no idea why it has been uttered in that way, I choose you as the final arbiter.

Thank you.