For what it's worth, I have a Vito VSP-stencil Yanagisawa tenor from 1980, and it looks very similar to the pictures on the CL ad you linked...though mine is not pristine. Guys claim the Yani stencils don't get all of the goodness that the Yanagisawa-branded instruments get, so let's say the one you are interested in is similar or better than mine in some respects, and its definitely in better condition. My point is this: I owned a T901 and played it side by side against my VSP for several months and really couldn't detect any significant difference between the two. (I also had a T992 and T991 and they were very different than the VSP and T901.)
You asked "Would I be doing myself any major disservice by getting this instead of a 901 or TWO1", and I'm suggesting the 901 might seem very similar to you as well. But the asking price is creeping into the neighborhood where you do have other options, Yanagisawa and other brands. You would be paying a premium because of the condition of the instrument, which I believe is money well-spent, up to a point. (I wouldn't buy a collector-grade closet-queen...I am not a collector.)
If you 1) play the instrument and like it, and 2) can make a deal you feel good about, then I say move forward. Call me Captain Obvious!