Hello,
Before going deeper into this, I think we should notice that the blade in the painting DOES NOT FIT the scabbard where it is about to be inserted in!
So the recurved curvature is more likely the result of a painting error.
The painter started with a curvature, but then realised that the curvature wouldn't bring the tip of the blade to the opening of the scabbard and since he couldn't simply erase the blade and paint a new one, he simply made the adjustment to the curvature. As simple as that.
An indication regarding the skill of the painter can also be derived from the position of the hand holding the sword...
Alex, the sword in the museum photo has an obviously bent & twisted blade and is not at all recurved.