How accurate is the seatmap on ExpertFlyer with regards to which seats are taken and available etc?

Departing Airport: London, EN, Great Britain (UK), Heathrow Airport (LHR)
Arriving Airport:Sydney, NS, Australia, Kingsford Smith Airport (SYD)
Depart Date:04/09/09
Airline:Qantas Airways (QF)
Flight Number:320
Class Code(s):Y,F,J

If you only query Y,F,J it seems to only show about
18 blocked seats in Y
12 occupied seats in y
F completely occupied bar one seat
J 1/3 full.

Now if the airline uses so many possible codes i.e for economy as shown below...

B ECONOMY
BN ECONOMY
H ECONOMY
HN ECONOMY
K ECONOMY
KN ECONOMY
L ECONOMY
M ECONOMY
N ECONOMY
O ECONOMY
Q ECONOMY
S STANDARD
T Premium Economy
V ECONOMY
X Economy - Award
Y ECONOMY
YN ECONOMY
Z ECONOMY PLUS

You can try and enter all the relevant codes to the query but half of them return errors in your search.
How are you meant to get an accurate view of occupied seats?

why cant you just see a 'show all' view so you dont have to enter the code class in?

To me unless it is 100% accurate it would seem almost pointless.
Theres no point aguing with airline or booking staff that you have seen 4F is free and you would like to request it if it isnt.