Oh now I know why I never notice this, I use the app and we have enough extra space in the app never to notice this issue if it even happens.
Thinking out loud here…
On iOS 13 with visual viewport api we are going to be able to eliminate the entire ugly iOS hack (and much of the iOS physical keyboard hack)
In the interim I guess we can adjust some numbers in the hack.
The last changes in the safari hack file came from @joffreyjaffeux who added mutation observer and shuffled a bit, can you investigate this Joffrey and see if you can repro and correct it?
Another thing to think about is that we can live in the future with the app, cause it can simply provide a simulation API so we get a non hacked up pixel perfect fit. Not saying we do this right now @pmusaraj but something to think about depending on how good visual viewport api ends up being.