You're correct. I've read through the '91 brochure – the term "Direct Drive" was used regarding the performance of the rear triangles, although this seemed to be applied generally across the Orange range. Sadly, there's no visual clues to confirm the decal.
In the '92 brochure, "Powerstay" decals were applied to the stays. I think this refers to the aluminium frames though. This decal uses the same classical serifed font Orange used at the time, with an orange in place of the 'O'.
Surely, somewhere in the expansive hinterland of RB there must be an example....