Layered approach for privacy is just fancy word salad for opt-in privacy which is known to not work at all and even endanger people through wrong assumptions.
Discussion
Most humans in the future will not own on-chain UTXOs. It will be layers on top that service the billions of people in the future who will own Bitcoin. Something like CTV can allow them to share their UTXOs collaboratively so they can access lightning channels. For them it will be private by default because their entry was via post Bolt12 Lightning.