Just my opinion, but I think it is because the lifter sits horizontal and allows the oil to drain out. Would love to hear from someone with an Accusump on their engine to see if pressurizing the system before starting made this go away. I've worked on them since they were first introduced, and they all have a slight tick. Also have customers with well over 400K on them with no issues, but still the start up tick. I have seen first hand (or actually heard) that anything but a Mopar filter increases the severity and length of time to pump up the lifters.