From what I understand of JZ's process, you collect the trub, store it and let the yeast settle, pour off the liquid (beer), add sterilized liquid (boiled and cooled water), shake, let sit for 15 minutes, then pour liquid/yeast suspended portion back into the new wort. Pretty simple ...
If I am brewing the same beer as the one that the trub was collected, why would I need to pour off the liquid just to add liquid back? I would think that I could just swirl the settled yeast back into solution, let sit 15 minutes, and pour the suspended yeast/beer solution into the new wort. The dead stuff will still settle out first and the added beer isn't going to add any off flavors since it is the same beer anyways. Any reason not to simplify the process as suggested?
Yes, there's a couple reasons. The left over sugars along with the fermented sugars can lead to spoilage. If you've ever done a starter, let it floc & then just sit there, you've seen the liquid slowly become darker. The braver souls who've tasted this know the sourness & funk can only mean brett, lacto, pedio & who knows what else have invaded. If you rinse, let settle, decant & repeat a second time you'll have a yeast sample that can sit unspoiled under sanitized water for a significantly longer time. I have one that I've had in the back of the fridge for roughly 20-21 months now; I can see the slow decline, but I guarantee that I could brew with it given a few days notice. I've had the same strain go bad in a few weeks after I finished a starter & placed it in the fridge.
Mainly, you want that sterile water rinse to get rid of bad yeast cells & contaminants, such as trub and the like. In my process I rinse and do cuts during the process:
Collect your yeast, let settle.
Decant & add your sterile water. Swirl.
Let set for 5 minutes or so. Decant into 2nd sterile container leaving behind most flocculant yeast.
Allow to settle for another 25-30 minutes, decant & discard the top liquid. This is the least flocculant yeast.
Change the times to get the cut you want out of your yeast.
Also, you rarely pitch directly back into fresh wort rather than doing another starter to get the best count of healthy cells. The more you reuse yeast, the more you have to be careful of the mutations, etc. The more generations on my yeast, the more careful I am to the cuts I'm using (I'm pretty damn picky & tend to select <5ml to grow for my next 12g batch).
I don't see any reason why your process wouldn't work, but I also see the reasons why I take the extra steps for starters/storage.
(BTW, I'm a little tipsy after a real bad morning at work & then coming home to a bitchy lady. Take your salt with a grain of 'Shut the fuck up, Lee'. She certainly has.)