My statement is not incorrect at all. When you block a device, it will be blocked from the cloud services necessary for Google and Amazon assistants. Are you doubting that?
Unless you are saying that is wrong, then HomeKit routers have the tools to easily block Google and Amazon-compatible devices from functioning while Apple HomeKit devices continue to work. Therefore, Google and Amazon ecosystem is blocked.
I did not say anything about defaults, per device or other IoT. You are reading something that I didn't say.
So you are saying that, big reveal here: IF you turn on "Restrict to Home" on your ecobee (say), you will be blocked from using Alexa on that device until ... you go and turn that setting off for that one device?
How is that any more sinister than any other router setting? I mean, I have a plain jane Orbi network here, and can go do the exact same thing to my ecobee today and lose Alexa access (and, as the warning clearly says, I would also lose access to the weather downloads etc). On my router, I don't even get a warning, just a big "off" switch.
So, yeah, turning on the "don't let traffic from this device out of the network" makes it not able to contact stuff outside your network. That's kinda doing exactly what that setting says it does. If you don't want that setting, then don't enable it!