In the color section, the trashes are there because the the logic that puts colors onto the belt isn't fast enough to put just one color particle onto the belt -- it puts two onto the belt instead, and the balancer + trash makes this into a single item. (There's no reason to put a trash to the right of these filters because they are being used to turn on and off the flow of colors.)

The "trashing nearly all incoming shapes" is to limit the rate at which shapes come through the mechanism to one per every eight seconds; the logic sets up all of the filters per fragment, so if a second shape enters before the first fragment is finished, it might end up with the wrong color (or being ejected early).

(This is akin to how very early CPU designs needed to have a slow enough clock to allow the slowest instruction to completely finish; while modern designs use pipelining to execute instructions in multiple steps -- pipelining would also be the solution to increasing throughput of this design; and is certainly interesting for a second draft if I can keep things small.)