The link shows the North axis is tilted away from the Sun in Dec (3/mths), thereby no day-light, and in June towards the Sun (3/mths), thereby no nights, but in the March and Sept position the North axis gets half light/half night (6/mths), under this failed THEORY the Earth is flat.
That doesn't seem to show proof of a flat Earth to me.
I agree, I think he is claiming at the fall equinox the north pole will receive 3 months where the sun is exactly on the horizon, as shown on the picture. The way I understand this, it is not true.
It's only on that exact day (Sept 22) that edge of the suns rays will be exactly over the north pole. On every day after that, the position of the earth in orbit around the sun changes so it slowly moves closer to the position shown in the Winter Solstice.
From a person standing on the north pole's perspective, as the Fall Equinox approaches, the sun will appear to circle closer and closer to the horizon. On the day of the Fall Equinox, the Sun will be at the horizon for the entire day. On the day after, it will be just below (you will probably still see the glow over the horizon, but it will fade as the days go on). The next time the Sun will rise above the horizon from the perspective of a person standing at the north pole is the Spring Equinox, 6 months later.