I really doubt they have targets. They're sort of obliged to ping you if you're going over, and with camera footage of you pulling a top gun fly by, it kinda leaves them a little vulnerable to just let you go.
And as for the other thing, if you look at it, it really does send a mixed message. P1's lose their licenses for anything. Anything. A learner gets more leniency (although I don't really have any problems here), as do P2's and fulls. On public holidays there are double demerits to discourage you from speeding during that period. so wtf are the demerits for on every other day?
I've always governed my speed by telling myself "don't go faster than you're willing to get caught". During double demerits it means stick to the limit, every other day is 10-15 over. When the same offence carries 2 different penalities at 2 different times, it does send a message that it is more acceptable at one time.