I agree with your perspective here and also think this qualifies as "from scratch." Would it still be "from scratch" if they bought all the components they used in this write-up as one kit?
I think in the 'things' space there is the notion of 'kit built' versus 'scratch built'.
It gets even a bit murkier when you think about wood working. Over the years I've built a number of things where the "plans" were in a magazine or an article and bought all of the wood, cut it to size, and assembled it "from scratch." but I didn't actually design it.
What I like about the keyboard article is that he designs the enclosure, provides his own wiring, and keyboard scanning software/firmware. So for me that qualifies as "scratch."