The app doesn't control what people do, it just makes recommendations based on busy segments, based on data which is already obsolete by the time it's being used. Ultimately the lemmings will do whatever their lemming brain tells them to.
(That is, assuming the app doesn't actually try to spread people around the various routes. But I doubt that any app maker wants to assume responsibility for that.)
Ultimately traffic apps are mostly useless. You can't "solve" traffic congestion with apps any more than you can make water flow faster through a pipe. Congestion is constrained by available road space and choke points. Google Maps is mostly an excuse for Google to collect location data, with a thin layer of features on top to make it seem worthwhile.