Yea on my Android app, pages such as Twitter and pdf cannot be loaded and displayed properly, and I have to open browser to see the actual content.
There's a way to work around this using Android firefox (or a fork) with Android pdf.js extension. Mozilla is making this hard by not blessing this extension even though it uses one of their own developed pieces of software.
For some reason Android app devs think it's perfectly normal to not be able to open pdf's in a browser tab.