I'm guessing it was installed for ambulatory wheelchair users
I think they are installed for legal reasons as level access is required by law, but are as useful as a chocolate teapot as you need to be able to walk as well as climb down steps/ladders for evacuation reason.
The reason that I mention this in my last post, is because I know that the rules for riding requires you to walk has been a rule for a good few years, and I've known that as I've mentioned this many times over the years on this forum.
So I don't understand their claim that they have visited Alton Towers for many years without any issue. Their claim just don't stack up. If they are telling porkies to make a fuss of this, then it makes me wonder what else that they are claiming with the way that the staff have treating them is what really happened?