IF they design it to work that way it can. Do you trust the manufacture to do that though? This is not only do they need to design it that way, but also that they need to ensure it works in all the edge cases. I've been in software long enough to know there are a lot of weird edge cases nobody thinks of that are then missed for years.
If you toggle or otherwise manually manipulate a light switch, surely it is physically disconnecting the circuits? I don't see how that mechanism could ever not work, absent mechanical issues.
A smart switch cannot be a toggle. It needs a relay of some sort so that it can be controlled by software. There is a switch you control, then something, then the relay. That something needs to work.
I use Lutron so I'm less concerned about obsolescence... but yeah. Pretty much every smart light switch I've ever used is just a normal light switch with additional networking capabilites.
