I recently bought a Guyot Designs SS bottle because I liked the solid way it’s built.

I already owned a SS "sport" bottle by Isosteel . The Isosteel is lighter and has straight sides, but has one significant drawback: the bottom has a second piece of steel pressed or glued on, presumably to give it a stable base for standing up. If I needed to use the bottle as an emergency kettle or pot, at the least this double layer would slow down the heating process, and at the worst would pop off (perhaps explosively). No such problem with the Guyot Designs bottle. What is the objection to a non-cylindrical design?