i don't doubt you at all about the 18kph. my hatch used to have the doors lock at around 25-30kph. the wife tells me here doors lock at around 45-50kph. the speed that the halo engages must have a varyable setting by the dealer.
There are two (well, three) settings.
HALO off
HALO on - locks at 40 kph (which is where mine is set and I'm happy with that).
HALO on - locks at approx 15 kph
I may have mentioned this before but my party trick when someone is in the car who hasn't been before is to lift my left hand off the wheel at about 35 kph and snap my fingers as I reach 40.
Gets some interesting reactions.