How are you going to get that dust?
With Cobblestone.
How are you going to get that cobblestone?
With an early game cobblestone generator.
Why not make that generator efficient, so you waste less time grinding cobblestone, why not design that cobblestone generator in such a way that it can be used in the future for your cobble generating needs (basically it'll grow with your capabilities)?
That line of questioning is what this particular design was designed for, and in my opinion it does it very well.
As for the piston thing... meh? This design is elegant, looks decent (and can be made to look much better quite easily), and will function quite well indeed throughout the whole game. One of the few designs it probably won't work with is the piston clock. Oh well? It doesn't take THAT long to get the materials for a block breaker, which works quicker than the piston clock, and is easily fully automateable, AND can be replaced with a transfer node, in place. Plus you can't beat the compactness of this design while maintaining its reliability and efficiency.
Also, pistons are loud and vanilla clocks are laggy.