Thats not abnormal. Real wide angle photography exactly looks like that. Photographers refer to it as barrel distortion.
A fisheye has 180 degree view so it will curve the most. A 'wide-angle' will be somewhere between the fish eye extreme and the 'regular' angle that we are used to (around 28mm focal length)
here's my G4 shooting through a 0.45x wide angle lens. You can see the curving edges.
if you ever have the chance to hands on the camera on a Sony Z5, you'll also notice its angle feels wider than normal, cos its lens is around 24mm which is wider than the typical smartphone.
You will also notice the image quality worsens towards the edges, that's another shortcoming of wide angle lens and i wonder how the G5 copes with that. Actually I want to see how the G5 does wide angle in low light cos I keep hearing rumours that its low light specs (OIS, aperture) arent as good as the main camera.
All flagships went down the 1440p QHD slippery slope since 2015. Our battery life will never be as good as it used to be unless every phone has the kind of battery size that the S7 edge has.