I can see some similarities from the front between the G6 and the S6... and even the Note 5 as shown below and other Samsungs. You can see it too in the Pixel as far as shape. But I think what may really make the Samsungs look closer is that you can see the Samsungs already have a small chin and forehead on their phones along with the thin bezel shining around the glass.
So if you could imagine Samsung never going with the curved glass look and sticking with a flat screen, evolving the look, eliminating the home button to reduce the chin that much more as well as the forehead, I have no doubt it would look exactly like the G6 front.
The back of the G6 with the dual cameras and center/home button looks nothing like the trademark Samsung looking single camera bulge in the rear.
I bet there are many out there wishing Samsung didnt go with curved glass and thinking that's exactly the how I want the phone glass to look in a Samsung.