Take this example from
GWS (the only one I could find from a quick google search that actually breaks down their numbers at all), the headline is: GIANTS Hit 20k Members in Record Time, not: Giants hit 20k members, 4,812 of which are 3 game Canberra memberships, they are intentionally lumping at least both the season ticket holders and Canberra members together, they're withholding important pieces of information because it's a better look for their PR and marketing in an attempt to try and convince the average Joe that they have 20k members in the traditional sense i.e. season ticket holders and cause they know that journalists will then take up that 20k number and not distinguish the Canberra members making it look like they have 20k members in their main target market of Sydney and are doing better than they actually are...
Almost all the numbers you see in this thread, in the media, or wherever are aggregate numbers made up of multiple types of memberships sold, they aren't broken down into categories or restricted to just one type of membership and I'm sure you know that, and that in of it's self is intentionally misleading.
I'm sure they do, doesn't really matter though cause they still don't provide a breakdown of what is actually included in their public number counts to the general public and even if they did they still wouldn't be releasing that full breakdown of numbers publicly anyway.
BTW, if you are suggesting that most clubs don't count things like 3 game memberships or whatever in their public counts or even that it is or may be standard practice to only include full season ticket holders into their public counts then you are delusional, especially when considering that in the past club like e.g. the West Coast Eagles have claimed more members than their home stadium at the time could actually house...