Having been on park many times and not just at Alton Towers, just studying the app doesn’t often give the true picture.
You’ll often find the app/queue board say something completely different to what is actually true, sometimes for the good sometimes for the bad Smiler might say 60, when it’s only 20 but the other end it could say 60 and in the end you wait 120.
Being on park you’ll find this easier to find and see, of course sitting at home you don’t see the full picture.
Before the app you didn’t notice downtime as much, as wondering the park unless you walked past a closed ride you wouldn’t have a clue what’s going on. Now you can look at the app and see half the park shut on the app, wether that actually affects you or not on the day.