Nope. GM reuses RPO codes all the time. WS6 is "PERFORMANCE PACKAGE, SPECIAL". It has been used since 1974. I know this is accurate. I am a Software Engineer for one of the companies that provides Electronic Parts Catalogs to GM. You should see what happens with the mirror codes. They are re-used all the time, across several models, all with different descriptions.
Frank
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2000 Bright Red GTP