Site full - but not?? What is going on?

Arrived at Poolsbrook one day last week having booked for a few nights to break our journey south from Scotland to home. No issues when booking - not a full night showing anywhere for late June/ early July and not even a Low anywhere. As is my habit I checked availability the day before we were due to arrive just to get a feel of how busy it might be and was astonished to see that EVERY night on all types of pitches were full for the next 7 days or more. Couldn’t find anything happening in the local area when looking online and when checking other local sites even Chatsworth was not full over the same period. Imagine my surprise when we arrived to see the board outside the office stating pitches available today! Asking the site manager when we were checking in as to why the site was showing full on the booking system she said it was down to site management as directed by the club??? 
Why would this be? It was quite apparent that the site was about 2/3rds full at most whilst we were there but if anyone was wanting to book through the system they would not have got in. Is the club manipulating site occupancy in some way? It seems odd that Poolsbrook is one of the sites that no longer opens all year - is this because they are claiming it is not needed due to occupancy levels?
I find this most concerning because there must be a number of members who are notable to book into sites that they want to use and have to find other places to stay instead which must risk them questioning whether to bother trying to stay on a club site in the future.