Now there's a question......
I'd say that as it is a speed limit point then that defines the speed you should be aiming for at that point in the arrival. I fly the airbus, and left in managed speed, the magenta circle (deccel point) is a little before the SLP, so the aircraft should be down to that speed by the time it passes the SLP...
Analogy with a speed limit on the road, you shouldn't start to slow down after passing the "30" sign as you are effectively busting the limit. Now I'm starting to sound a little anal !!
As with all things like this, applying common sense usually prevails.