Correlation between practice tests and actual GMAT

Firstly yes there are plenty of born good test-takers who, with just a couple of weeks of studying, can score amongst the top 1%.(Read as 99%tile)

But not scoring 700 on practice tests doesn't debar you from scoring a 700 on the real test. When you read experiences, do so with a pinch on salt and do not blindly believe that what worked for others will work for you or vice-versa. Reading experiences of other people provides motivation but can also de-motivate you don't read it in true spirit.

FYI, even Math and English wizards cannot ace the GMAT without some studying.

So your challenge now is to keep yourself motivated and do not accept defeat at any cost. Don't think about what others have done, rather think about your own plan of action from now on. There is plenty of material + help available to take anybody to 700 or even 750.

All the best!