I had the chance to ride both directions last night. As I was taking some photographs just inside the exit side of Kings Cross Station before heading in I did see/hear some confusion from guests walking up and not understanding why they needed a park hopper just to 'ride the ride'.
This is the first time I'm aware of that you needed any sort of a park-hopper ticket just to 'ride the ride' and it's going to take some time for people to get used to the difference. I haven't looked at the park guide maps yet to see how they are explaining it but it's a very new concept that is likely to cause some confusion for a while, especially for folks who are not Theme Park ninja's following every detail of these sorts of things.