Pronunciation vs PronunciationS
Is 'pronunciation' in singular or plural? The Cambridge dictionary says : noun [ C or U ]
https://dictionary.cambridge.org/dictionary/english/pronunciation

E.g.: Are their pronunciations accurate in that video ? (Is this example grammatical?)

Thank you.

Question

Pronunciation vs PronunciationS
Is 'pronunciation' in singular or plural? The Cambridge dictionary says : noun [ C or U ]
https://dictionary.cambridge.org/dictionary/english/pronunciation

E.g.: Are their pronunciations accurate in that video ?  (Is this example grammatical?)

Thank you.

Answer

Is their pronunciation accurate? Any number of people.
,
You can make up a sentence to make almost any uncountable noun sort of countable, if you work really hard at it. Such as talking about multiple instances of something. Generally, though uncountable is uncountable.
I am not aware of any normal use using pronunciation as countable.