The answer is complex:
This is what you may found in the so-called "specialized litterature"
"Marking a radical departure from Junkers’ patented corrugated Duralumin skin concept, the K 47 was initially built with a completely smooth skin, although old habits die hard, and production versions incorporated corrugated sections."....
"In stark contrast to Junkers’ traditional square-angled corrugated skin, the K 47 prototype was given a much more elegant and streamlined smooth skin throughout, although the wings and the tail surfaces of production machines incorporated corrugated skins. "
However a careful examination of photographs does not allow to note such a presence of corrugated skin on the horizontal surfaces of
Chinese machines - only on the vertical tail surfaces. BUT on the
Swedish machines the surfaces of the main wings and the dive brakes were definitively corrugated.
Chinese

Swedish

