They're using an ultrasound machine that calculates the age based on measurements, they aren't guessing the age by looking at a picture so when they tell you what week your baby is measuring, you can be assured that it is accurate as far as how many weeks the baby is measuring. 

Yes it does

This was mine at 8w 1d

Yes, babies are very very small at this stage and aren't human looking just yet

Looks about right to me. Here's my 9 week one.