Site fully booked, or not?

We are staying at Moreton in Marsh for Easter, and having a nice break.  According to the website in the week leading up to our arrival on Friday the site was fully booked, so if we had not already booked we would have assumed no point trying.  However throughout our stay there have been 5 vacant hardstanding pitches within sight of our van.  We noted the same happen at New Forest last year.  

I always use the online booking system, am I losing out on sites I want to book by assuming (it seems incorrectly) that the information on the website is correct? I don't think I should have to ring sites as well as using the website, that is not user friendly.  The booking status of the site should be real time and up to date if members, wardens and the club office are all using the same system to make bookings,