How is it fishy? Native app delivers a 'better' experience and lets Facebook do the things that make you (supposedly) use it more, like push notifications and location tracking, sharing photos + videos, etc.

I just don't know why it thinks any of this is better.

I also hate the fact to even look at my messages I have to "refresh as desktop site" on iOS

You don't know why anyone would think that a native app can deliver a better feature set than a website?