Was the Opel GT-W (1975) prototype based on the XP897 GT?

Stefan Heins of ALT-OPEL Interessengemeinschaft von 1972 e.V. noticed that the European Opel GT-W from 1975 looks a lot like the experimental show car XP-897 GT.

Stefan writes:

Dear Mario,

I am the editor of "Der Zuverlässige", the magazine of the Alt-Opel IG. Opel focuses this year on the Experimental GT 1965 again and thus we decided to do some research. There is one orphan that does not fit the picture: the GT-W 1975. A year ago I met the designers George Gallion, Erhard Schnell and Friedhelm Engler. We looked at that GT-W and noone could remember who had designed it. George agreed the shape was looking too old to be 1975.

Coming to XP-897 GT, this one looks similar to that mysterious GT-W. It is a mockup and has been in the works collection (Opel Classic) since 1975. No documents about any prototype having been tested on the road or at the Dudenhofen track ever. As I know some people who have been testing way back then I am almost sure there has never been an Opel GT-W fitted with an engine. My question: Do you think it is possible GM has shipped a mockup of the abandoned XP-897 GT to Opel, have it badged and shown around at the fairs?

Please find enclosed the latest edition of our mag and some pictures of the GT-W. No cooling vents, a slightly different shaped back and a different front bumper - that has been drawn for XP897 GT as well.

In Corvette history there is nothing known about the XP-897 GT being reused as this Opel design?