(they know the activity on each servers, the population of each (with inactiv character that could become activ), and the number of houses is easy to count... 540 at personnal houses release, 2160 during HW, 2880 at 4.1, 4320 today. For activity, luckybansho helps us to get an idea of how much character are activ per server... 550k activ people, 66 servers => 8.3k per server.)
About simple mathematics. we can easily count how much houses :
1080 at personnal houses release (or not sure if houses 31=>60 did existe at 2.38 or added just after but not a real difference)
2160 during HW,
2880 at 4.1,
4320 today
They know how much character, FC. they can have a quite excellent idea of the activ part.
With luckybansho scan, we can see 550k activ character (600+ on period with the 96h free login... so i am more looking on the others results)
66 servers => 8k5-9k activ character per server (activ from luckybansho : getting at least 1 more minion/mount/level in any job between 2 scan)
In reality, most japanese server are under this, and european/american server are many time over (with high spike for ragnarok/balmung and other like those) ... But easier ton consider same for all
We see that we have 1 house now for 2 activ character. and there is the FC matter then...
SO YES they did the mistake knowing it was a mistake.