The definition of smart home is very loose at best.
Most say it’s smart if you can control it from a phone. I’m not so sure about that. (As you also imply).
I remember back in the 80’s or early 90’s.
My grandparents had a house they could remote control by landline phones.
You called the phone number of the house and the “smart thing” answered and you could by pressing a code (I assume) turn on the relay it was connected to.
Back in those days, that was smart. But today it would just be hard to use.
Same thing when we look at “smart” when it comes to phones.
Smart phones from the early 2000’s wasn’t very smart.
Sure there was apps and you could develop stuff in them but what really made them smart was (in my opinion) when they joined up with the same platform and the same apps.
That moved the phones forward a lot.
If we now compare that to smart homes.
Sure a wifi socket is smart but it’s not until you add it in a joint platform that enhances it from the socket to a something more that I find it smart.
The single sockets/lights are like the old 2000’s phones that you called smart but was limited to their own little sphere.
TL/DR: it’s not the hardware that is smart, it’s the software that can unite lots of different hardware that is smart in my opinion.