I think you do have to get the treasure. When I went through the Bevelle temple for some reason I stepped around the the place you needed to in order to the get the treasure (I think it was 3:00am and I was rushing to get to a save point), but I didn't get the treasure.

I went to the Anima temple and only 3 sphere's lit up... then I went back through the game and opened the chests in all the temples (but Bevelle), now five of the 6 light up.

I followed the instructions in the spoiler above and killed those who needed to be killed, but it still won't open up for me... I'd hate to have to start over to get there....thoughts?