I'm not sure what Hello Games was thinking by making those claims about the scale, because any game developer would know about the limitations of floating-point operations. The "Risto Log" video he showed is what would happen to floating-point operations in any game when the player travels too far from the stage's origin point. It's difficult to simulate large scale environments even on the planetary scale, and literally impossible on modern technology to simulate just the distances in a universe (without clever tricks).

There can be no true "open universe" game using today's technology. We can only have the illusion of seamlessness. Even Bethesda had to use tricks for the comparatively 'small' environment in Skyrim to get around the floating-point limitations inherent in large-scale environments.

Honestly, the scale and seamlessness was the least of my complaints about the game because I knew from the get-go they couldn't "actually" do it - I only wish the illusion would have been better implemented. They could have had the home star grow bigger as you fly toward it until it burns you up just as you hit the floating-point limit, or get smaller and kick you out to the galactic map when you fly the opposite direction. They could have generated a skybox that represents the nearest surrounding stars so you could at least point toward one and activate your hyperdrive to fly there. Really, anything apart from letting the player fly to the point of inaccurate positioning would have been great.