Halliday only reviews wines which are sent to him. Now some wineries with excellent reputations have been a bit reluctant to send wines in for fear they would not stack up. This is not good for Halliday, because he wants to have all major wines represented. What happens, he inflates the reviews to get all the wines - a silly system.
The wine descriptions can be helpful, but forget about the points (which basically seem to have a range of six (from 91 to 96).