With you 100% on the aeroplanes, balloons and Branson, Jack, and I'd agree with you on the Inspiration4 if it were to (somehow) hover geo-stationary at a low Earth altitude. But it doesn't; it moves.
The thing about the horizon is that, like a rainbow, it is only relative to a single, fixed, point of perspective. In an aircraft, balloon or near-vertical sub-orbital lob the observer's motion across the planet and change of horizon is imperceptible. At LEO velocity, however, what was "horizon" 20 minutes ago is now beneath you. Over a flat earth approaching features will simply come into greater clarity, over a round planet they will, literally, appear and disappear over the horizon.