I don't see any 'bubbles' in your photo.

Here are images from their website. The intention is to make this man made product look like natural stone. There would be irregularities in natural stone. You don't want it to look perfect.

I agree with the defect. None of their site pictures show air bubbles like I see in the middle rock in your picture. I'd reject all like that. And ask them to show you photos on their site with the same air bubbles.