MikeBass, regarding the Carvin preamp you're describing I say "it's about ####### time !!!". I, along with soundmen everywhere, wish all active preamps had that feature.
I personally owned two different brands of active basses that were made that way as stock long before Sadowsky did it. Surely among the couple hundreds or more other active builders there were others.
That's o/t though. I am not aware that Sadowsky ever claimed to have done it first, nor am I suggesting it. I do believe they were first to give it a new name. The effect is that it has become common use (around this small corner of bassdom anyway, where people have commonly heard of the brand), and by extension people seem to think Sadowsky came up with it first and that there's more to it than a simple passive tone rolloff.
In that latter point I disagree with Vik, because I suggest that if the name were actually more descriptive there wouldn't be so many people asking what it does and how.
Whether it was done on purpose for marketing benefit isn't my point either. It doesn't matter. The net effect has been as I've described it and in that sense it's been beneficial and clever marketing. That's my point.
"Passive" itself is not an exciting word, while "vintage" is very appealing to musicians. Especially if you say Vintage Tone Control as three drawn-out words with delay and a monster truck rally voice.