Here's how I understand the two idols at the same beach concept.Because of the One World theme, two tribes (Salani and Manono) were on the SAME BEACH. One idol was hidden in the womens' camp and one was hidden in the men's camp.
Sabrina found the HII in the women's camp but was forced to hand it over to a man (Colton.) Any guy knowing Sabrina had to give it to a Manono would understandably not put too much effort into looking for a HII they would not be able to keep.
With the tribal switch, the NuSalani tribe stayed at the "same beach" where both tribes started the game. Knowing the NuManono tribe had to move to another area, it should have appeared obvious the finder of the HII (still hidden at the old men's camp) could not give it to a member of the other tribe because of the inability to see each other.
As I stated in my list, it was a huge advantage for the four women staying on the same beach.