How about during the battle, where he goes towards the lighter parts of water and he still doesn't have a reflection? The closest he gets is the ripples around his shoes looking like a reflection, but unlike Aqua that doesn't cast his entire render as a reflection.But sora does have a reflection in that first picture, look at his shoes carefully you can make out the bottom of his shoes have been mirrored and are below where his shoes should be. It's more obvious in motion because the reflection ripples so you see the color of sora's shoes bleeding into the water and rippling.
Your second picture only supports what was just said that Aqua's reflection is seen because she is standing in the brighter areas of the water while Sora is always on the darker side of the lighting.
It may be easier to see in the archive of the stream rather than our recording of the stream (@ 32minutes)
[video]https://youtu.be/tORuUe1oIUQ?t=31m57s[/video]