Right theres not 65ml of SLURRY in a yeast vial/smack pack.
On the subject of trub as a percentage of east cake, I was in the habit of pitching most all my trub into the fermentor, just running the wort through a mesh screen to get rid of larger pieces of hops. I'd get a nice healthy inch of yeast cake. Recently I've begun colling and racking my wort off the trub prior to pitching, and I'm get about 1/3 as much in the bottom of the fermentor. Its much lighter colored and finer. Bottom line, I bet the slulrry volume recommendation is based on having the trub removed first so you'd be quite low on cell count if you don't remove trub via whirlpooling or some other means.
On the trub topic, I use DME to make starter wort and even with a short boil I get a pretty substantial amount of hot/cold break. This is the stuff that drops quickly, so even if you are relying on visual volumes in these things you might be over-estimating.
Finally, if you pitch a vial in 750ml of wort will it even double once? There was a discussion in Yeast about this, you might not get much of an increse in cell count with this method but it would at least get the yeast active and give hem a running start. I think there's something to be said for a "running start", in the few times I've done it this way I see activity sooner. Looks to me like there are cellular activities that take some bit of time to ramp up before even cell membrane component synthesis can begin. You have to make some enzymes and express the right proteins before you can make triglycerides and cell membrane proteins.