Or she drove around trying to decide where to put him.... so her cell phone pinged in several areas. She may have stopped in several areas for about the same amount of time.
Or she put him in the water, so they still have a huge area to search because of currents. (Which is where they seem to be focused on, the water.) Plus, she likely wouldn't have been stopped for more than a few minutes.
OR, she went out there, decided she knew a better place and changed her mind. I have heard nothing about them searching the dumpsters or areas around the places she was that day. That wouldn't have shown up weird on pings because she said she was there.
I am inclined to think that if a family member was involved they are correct in searching Sauvie Island. It's somewhere comfortable for them all, somewhere that Kyron loved to go. Could be a last "loving" act, even if unintentional to put him somewhere he loved.