It is SOP in interrogation procedures to separate the interrogees and then come back together to compare what each said. I didn't get that impression from the 6 hour ordeal on Wednesday - but they may have.
Yes, they are saying they went into the backyard - maybe soil samples are back - but they also said the bags were "full" - soil samples don't take up THAT MUCH room. I mean you don't need a bucket full of dirt. They had to have gotten something else - HEY! - maybe the "returned" gas cans as well?