> Will this mean your smart home will have unstoppable connectivity you can't turn off?
No. Thread is a mesh networking protocol for smart home devices. A light switch, window sensor and a dehumidifier can be linked together. The light switch and the dehumidifier could be far enough apart where there would be connectivity issue; using thread, they can talk to each other via the window sensor.
I believe they're using the IPv6 non-routable address space. The way to remotely access these devices is through a border router, like a HomePod or an Apple TV. And because it's an open standard, all of the big guys—Apple, Google, Samsung and others—have come together on this standard, making it easier to mix and match smart home devices that previously only worked in Apple's or Google's or whoever's proprietary ecosystems.
Probably not - although that's "kind of" how thread is supposed to work, in practice it doesn't because there isn't a standard way to configuration / key material between thread networks. This [0] is a great ELI5 article on the problem if you're interested.
These kinds of mesh solutions are rather omnipresent in IoT already, like ZigBee. Would am iPhone acting as a bridge do more harm than a smart bulb acting as a bridge?
How is that "unstoppable connectivity you can't turn off"? And why would Internet connectivity in IoT surprise us - that's what the "I" stands for.
Just a smart bulb itself is not really how you use that. For it to make sense you already have some kind of a gate/central device that you use to interact with the whole smart ecosystem. Such gate is often already Internet connected device (be it a Vendor specific hub, Home Assistant etc.).
An iPhone can do harm here as much as my weird Netatmo hub I have to use with my radiator valves...
Depends on your definition of "forces" - the protocol enforces ipv6 addressability, and has the concept of a "border router" that transports messages from the network the BR is connected to to the thread network.
Presumably the fear here is that iPhones/ipads/macs will be border routers by default and since they likely have internet access they would "force" the system to accept messages from outside the mesh.
is apple enabling a bunch of nest/ring/foo business models?