Yep, I agree they should make the app consistent with the website. It's extremely frustrating.
I try not to use it for ADRs either, but I saw Ohana was available while on my lunch break yesterday. Well the mobile site was loading at a glacial pace so I went to the app. When I tried canceling my Trail's End reservation for the same time, I got errors saying it was unable to cancel and to call to cancel it. Well of course after several attempts to cancel, the Ohana reservation was gone and a few minutes later I got an e-mail notification that my Trail's End was canceled. Luckily Trail's End isn't the most popular place, so it was no problem getting it back... but I certainly wouldn't take chances on a high demand ADR!