“Walkable” has never meant “has sidewalks.” It means the neighborhood’s denizens can reasonably walk to meet their day-to-day necessities. It has always meant that.
In the US you tend to find this in places that were built before cars but with sufficiently high property values that rearranging the buildings to widen the streets doesn't make sense. See parts of Boston for example. The places that are both old and wealthy tend to have streets that are pretty much local access only through size alone.
In montreal there is an extensive system of back lanes, and I did a lot of my walking there, no sidewalks. The lanes were shared by cars but they were slow and infrequent.
Nonsense. Interstate Highway 90 is quite unwalkable due to its lack of sidewalks.
You clearly have not seen some of the highway interchanges in Olympia, WA.
They aren't just neighborhoods, they're whole towns. Of tents. Walkable, but surely not safe.
;)