I think there were two white trucks - one: the Horman truck, two: the GK's truck.
IMO, I think different witnesses reported seeing a *white truck* parked in different locations (i.e. one witness said Skyline Blvd. and one witness said on the soccer field access road).
I wonder if TH told LE that she parked on Skyline Blvd?
And I wonder if a tip came in that reported seeing a *white truck* on the access road.
So, maybe LE doubted what TH told them about where she parked, hence the release of the flier showing the Horman truck parked in both locations.
I also wonder if after the GK came forward with his info, if LE may have begun to have doubts about the witness sightings & perhaps began to believe that what TH told them about where she parked was true (IF she told them she parked on Skyline Blvd, that is).
It's also possible that I'm completely off in left field. No pun intended lol.
ETA: I still think it's possible that the GK's truck on the access road may have been mistaken for the Horman truck.