The PostScript specification requires that the saved image width always be less than the image height. For landscape images (where the width is larger than the height), the image is suppose to be rotated to meet this requirement but include the comment "%PageOrientation: Landscape" to indicate the plot needs to be rotated back when shown. See a third of the way down the page at:
I do see that Encapsulated PostScript can have the width larger than the height. At this time, however, PyFerret only produces PostScript and not Encapsulated PostScript. I could add EPS as another format option, solving this problem by actually creating EPS instead of trying to use PS as EPS.
(This issue has been mentioned to me before.)
I do notice that evince now does respect this %PageOrientation and shows the plot correctly. I remember older versions did not. Are you seeing the rotated image when importing the plot into a document?