It's as you say. But maybe Aqua chose to believe for now because he needs a pause and get rid of the weight he's been carrying for so long, even if for a short time.
We know Aqua is smart and even if he tries to forget and move on, learning they plan a trip to Miyazaki right after that scene tells us the audience shit is going to hit the fan (maybe a pun in there hahaha)
And we even get several reminders of the sinister imoortance of that place, last scene included.