It's useful and from a MR point of view, it's the difference in searching a huge forested area (like in that article) and having a precise location to go to is the difference between 40+ people spending 8 hours searching and 3 people getting there in 30 minutes and being able to render immediate care. MR are able to find a precise location from your phone but only if you are actively co-operating to do so, cell phone triangulation doesn't give much of a precise area whatsoever, unfortunately, though it is better than nothing.
Also, it's super quick. Open app, press 'locate', press the phrase with your finger to copy it to the clipboard (or say to an emergency operator on the phone) then you can do what you want with it. Takes about five seconds. Because it's so quick, when you set camp for the evening you may want to send a text to someone to let them know where you are - and then they in turn are more likely to use that phrase on the website than a string of co-ordinates. I think that accessibility/speed is the reason it is worth using.
Obviously it isn't going to be as useful for those of us who can read off grid references, lat/long and have people to communicate to who can understand those things - but as a more accessible tool for casual walkers as well as offers good reassurance if you're planning a more remote trip yet have the ability to send sms.
For those who use ViewRanger, you're able to use the BuddyBeacon feature which allows someone you trust (who you have given a username and password to) to track you whilst on a walk/away, but only when you have a cell data connection. It isn't especially intuitive on their website either, so whilst you may have some joy with it once a person is used to the system - it puts a few extra steps into the chain - but takes such a minor amount of data/power I'd use the feature anyway just in case.