Zone has futuristic technology yet is unable to go down to classic, which pretty much confirms it is a fake representation of the land "below".
Therefor there is still no proof as to classic having a legitimate sky whatsoever and we won't ever have one unless they'd add a way to render the game in 3D or add a way to go to space and literally jump down to earth past the clouds and all
And yes ik I'm looking way too far into it lmao