Miismatching sky?

Yes.

Why?

Because the real sky was pale and blank, making this (there being so much of it included in the composition) a non-picture. The replacement sky adds enough interest to make the picture usable - just.

But it looks odd, because the sky doesn't match the brightness of the sunlit houses.
Surely you must have something more suitable in your vast collection of Shepprton skies?

Perhaps, but it's hardly worth the bother for such a run-of-the-mill, record shot.