It's not. Now I might not go for one of my neck-through basses with active EMG's for "vintage tones" as a first choice when I have four perfectly good Precisions (OK, so three of them are PJ's but I only occasionally use the JI also don’t get why a P Bass seems to be the prerequisite for vintage tone.
As for the Stingray, Cliff Williams of AC/DC has used one for years with flats, and he certainly doesn't sound like Flea live. His sound is big and fat without a lot of treble.
But certain basses just plain excel in certain applications. Even Cliff cut most of his best stuff in the studio with a Precision, although he's best known for using a Ray live because he can hear himself better with it. I tried my Dano and violin basses for my band's upcoming new album where I'm getting a big fat bass sound without much treble, and I went with my P with dead flats because it just plain worked better on everything. The other basses would have worked very well, but something just doesn't sound right with these songs and arrangements while the P was all business all the way through. And I've done many a gig on a P with rounds playing a wide variety of songs, many with so-called "modern tones," and never felt like it was out of place. Now there were songs I probably would have preferred to have a little more scoopy sound and a little more treble, but that's why I use PJ's with rounds and that's why a lot of folks like the Jazz. They just plain can do it all and excel at all of it. But the P by itself is so good with a lot of that stuff in its own right that I really don't miss the bridge pickup very often.
Way more important than the gear is the operator, though, and if you sound inappropriate to the music you're playing, I ain't blamin' the gear.

