I don't agree. Today you can push out packages to embedded device easily; even tiny <4MB rom devices like openwrt.
You can push out regular updates, but you have to be very careful. You need to have full testing environments and real lab units of all generations to test on before you push to production and realize you now have a brick on the roof of an 80 story building that takes a week to get a roof permit form.
The cloud stuff is gibberish. Today's cloud is rebranded hosted platforms. I agree, I don't see the argument of making _embedded like the cloud_ being meaningful either. I know on my embedded projects we had a tight ship pipeline and you need that for the reason stated above. Sure you can do that with Docker/ResinOS, and it might help with building a piece of that, but I have a feeling it adds as much complexity as it might mitigate.