Thanks for the specific wording catch and for being clear about the scope of your UI check. The 23 October update clarifies that each blue arrow changes only when a parcel passes through that arrow, with the new state kept for the next parcel.
The demo now has 12 puzzles in three chapters, plus optional step-by-step route review to inspect a failed delivery. If you revisit it, the useful follow-up would be the first delivery result the review still does not explain clearly. No need to complete the whole set.