I was also told by 3eb's management that Stephan wrote those songs. But whatever. It doesn't matter, you can believe what you want.
First you say you can recognize SJ's style, then you say you were told by 3eb's management......so which is it? And what would you expect THEIR management to say, anyway?
For me, it's at best a curiosity who wrote what. The differences stick out more to you than I. For me, I think there is quite a blend, which to me is a sign of a great producer. Mind you, I'm not a 3eb fan, but I've been a fan of music long enough to recognize that while the lyrics got a bit deeper on Harmonium, the songs did not make a serious left turn that would confuse the songs with that of Elvis Costello or Neil Finn.
Do I believe that SJ wrote the majority of the songs on which they collaborated? No. My gut instinct is that he wrote a bridge here, a chord there, etc., which an album producer often does. And he deserves credit for that. Add to this that they were a couple and most certainly influenced each other, likely played chord sequences to each other, and that is what you get....a collaboration. The songs fit right next to the other VC songs, yet are different enough to make one say "F**K! I had no idea there could be so much variety on a modern pop album!"
Stephan did a f-ing brilliant job with this album, and it was a tragedy that it was overlooked. I don't know what he wrote or didn't write. I do know that this was one of his finest moments on all fronts.
Dan/NS