I'm not sure why you'd assume its a permanent 'enhancement' especially when you saw it on the web - there's no conceivable reason why they would intentionally take it off the app, but leave it on the regular web version.

Though I have noticed the app can be buggy with expert mode. I can't count the number of times the app will price an itinerary in say, S, or W, but expert mode when looking will show 0s in every fare class, Y on down.