Own a general purpose computer you can run arbitrary software on, not just corporation and government approved software? You're clearly a money laundering drug trafficking child molesting terrorist.
I used to think he was just paranoid...
Don't doubt it for even a second.
His mistrust might be about the phone's owner and the recording apps they might use, more than the smartphone itself.
Socially it's much safer to direct suspicion at "the smartphone" rather than the people invited to your house.