Yes, they could whisper their review. Doesn't sound like a very fun or energetic review though.

Yes, they could show the inside of the place, but that's not what they're reviewing, they're reviewing the food.

No, it doesn't impact people in the place too much. Unless they might be on camera and made to feel uncomfortable. That could cause issues.

I'd say someone politely and quietly doing a food review in their car doesn't impact your dining experience at all. Fully.