You know when you watch a movie, or a documentary, and the scene is at sunrise/sunset - and they include a time lapse of the sun rising/setting … but in fact they’ve used a sunrise for sunset, or the other way around … and reversed it? It shouts out at you!
Added skies do the same. A sky full of cumulus that manage to not cast shadows, or an almost clear sky with shadows of cumulus on the ground.
Even the sun direction can throw the whole thing out of kilter.
Therefore, what’s there plus a plain blue in the missing bit is better, imo.