You have to remember that a lot of magazines back then would post rumours to sell copies and without the Internet as it is now you could get away with a lot more. I am not necessarily saying it did not exist, but a PPC based expansion card is unlikely IMHO.
SOJ (and therefore AM2 as well) had no idea the Eclipse upgrade cartridge even existed until long after their American counterparts had abandoned this project in favour of their design for a new standalone console, dubbed Black Belt. Internal knowledge certainly didn't occur within Sega's Japanese headquarters until long after development of Saturn Virtua Fighter 3 had started - following Yu Suzuki's announcement at the Power Up conference in November 1996, where he also revealed Fighters Megamix - so it's not as if this conversion would have been able to benefit from such hardware, anyway. Really, it pains me to read all those misleading rumours about Sega's activities during the 32-bit era, since it's clear many still persist, and I seem to recall SOE executive Andy Mee even being fired after he gave out false information concerning the Eclipse, claiming it would launch with VF3 for the RRP of £79.99 when this was ultimately not his decision to make! Apart from not VF3 using this US-designed accelerator, which actually featured 3dfx technology as opposed to a variant of the same PowerPC solution as utilised in the Model 3 arcade board, Eclipse was intended to fit into the expansion slot normally reserved for the Video CD card as opposed to the port commonly associated with the Backup Memory device. If anything, I suspect journalists simply confused Eclipse with the 4MB RAM cart that did come out of Japan, albeit again completely unrelated to VF3, confirmed by one of the development team to have run on a stock console, as did AM2's prototype of Shenmue. Similarly, I remember quite a few magazines disclosing "world exclusive" details of the memory booster that Tekken 3 would require on the PlayStation, despite the fact Namco had always planned for this game to be less of a graphical leap forward than something like its main rival purely to aid the inevitable conversion process. Don't you just miss the days when supposedly professional writers could get away with these kind of unfounded stories... in physical print, no less?