The iPhone could be a Thread border router, but it probably shouldn’t be
The iPhone could control Thread smart home devices faster
Thread could replace Bluetooth as a way to connect peripherals like the Apple Watch to your iPhone
Thread would be fine for most smartwatch uses but not for audio streaming
Thread might just be a bonus radio
Thread is a Smart Home protocol. It’s like Zigbee and Z-Wave but different. Hopefully it’s actually going to become the real winner in the smart home world along with Matter.