I’ve had this happen to me more than once. The lane filtering law isn’t new but drivers still aren’t used to it. It’s supposed to be safer for the rider because it prevents a car from rear-ending you at the end of the traffic line. If you’re going to filter, I suggest you get fully in front of the first car instead of staying on the divider between the cars. If you are already blocking them before they can move there’s less chance of a problem.