It really makes perfect sense.
He is guilty in your eyes regardless. So what happens if he talks.
The police go through every effort to get him to contradict himself. The minute he does that, he is now guilty of lying to the police. If she walked out of him and he thought she was safe from the 24th until the 11th, nothing good can come from talking. It will only make you look worst and the police will get you to slip up.
The mom gets an text from her daughters phone on August 1st, easily traced to Yosemite. The van and BL was back in Florida on the 1st.
He would have to drove the van back to florida. Caught a plane back to California, then traveled to Yosemite to send one message, hope a plane back to florida.
That is the problem with this case. He could not drive that distance in 24 hours. He could not really fly that distance in 24 hours.
If the texts on the 24th and the 30th are from GP's phone , then BL could not have been
evolved. If those messages where sent those message were sent from anywhere, lets say texas and florida, BL would be in hand cuffs and arrested.