In the real world, the descriptivist realizes an individual's pronunciation of the concept labelled Jac/Jack/Jacques/Jacq/Jak/etc. depends much more on the their personal context and stylistic choice than the spelling used.
I've heard many folks (American and otherwise) pronounce "Jack" many times in my life, and the range of utterances very comfortably includes Pépin's own "Jacques".
Then you have absolutely no ear for this kind of thing, unless you're including non-native speakers, which would be dishonest at best.
I'd love to be wrong, because I'd learn a new thing. Please, educate me.
Nothing quite as weird as someone accusing me of not knowing how people in my own country say my own name.
The amount of misplaced confidence in this form is just absurd sometimes.
Anyway, sorry to have upset you.
They're not, though. The French pronunciation of 'j', as in the word Jaques is /ʒ/. In English, 'j' at the beginning of the word 'Jack' is pronounced /dʒ/. And 'Jaak' makes me think of Dutch, where that 'j' is pronounced as /j/.