I think its just a case of different peoples interpretation of the word 'Legend'.
There are a number of cars in the RS scene that are legendary. The main one that springs to mind is Martin's. To me, that is a legend because of how far and wide you can read about it. All across the world in all different car 'scenes'. It really is the ultimate RS, most will agree. To gain respect from people driving supercars worth hundreds of thousands is the stuff of legends and it wouldn't look out of place on a poster on a the wall of a teenagers bedroom amongst pictures of Porsche's and Ferrari's. A similar thing applies to Rod's.
Oli's and Jamie's to me are the iconic cars. They have been on the scene for years. Done the results, look good and therefore deserve the term.
There have been a few RST/FRST's that have broken the 10 second 0-100 and into the 12's over the 1/4. How many of us can say who they are? Not many, I bet. Why aren't they considered 'legends'?
SOY was certainly a VERY nice looking car. I remember it from when it was practically standard looking, putting in a pretty respectable 0-60 time at National Day, many years ago, when it had 'Danger - Emits Flames' on a sticker near the exhaust. However, there are alot of RST's on the scene that look as good. Take Stevenebm's (which I know had some of the parts from SOY). That is one seriously nice looking RST.
For the record, a low-spec R34 Skyline doesn't really do big things in terms of performance until over 100mph. Until then, it is really a bit of a heavy bus. At 7psi, I would imagine that SOY was over 200bhp and quite driveable, with good grip, so would perform well. In terms of power-to-weight, in certain situations I am not surprised that it saw off a hefty car.
Thats my tuppence worth......