That makes sense, let's have a good vigorus start, and then do our best to undermine that start by letting the beer sit on a pile of dead yeast, and whatever else might be sitting in there.
There's nothing else sitting in there that hasn't been put in there.
Do you know how long it takes for a pile of yeast to die? You could let your beer sit on top of the yeast for a month, rack it and do another batch with the same slurry no problem.
How do you imagine that beer carbs up after sitting a few weeks in primary and a few more weeks in secondary before bottling? There is still plenty of alive yeast in there.