Before W3W, I once tried to report an accident and the emergency operator couldn't accept either lat/long or the A and B numbers of the roads involved. They wanted the road names or the postcode. The roads involved changed names several times along their length, and their names were quite common so were repeated in lots of places, and I didn't know their names at every place, even though I drove them quite often. I found it very stressful.
The problem with W3W is when emergency operators won't accept other methods and demand that someone in crisis downloads an app, and then tells the app the numbers that they could have told the emergency services. It's a non-trivial download, that users may have to pay for the data for, when actually anyone can go to the W3W website and convert any lat/long, postcode, address etc to a W3W code.
There are also systems built into any phone that should allow the emergency services to see where a smartphone call is coming from, but those don't seem to be used.
It's good if W3W can be added to existing methods of location, but it seems to be being added at the expense of other systems.