I am in the possession of an OpenMoko Neo FreeRunner which begs to disagree with your Chronology ! :-D


But indeed this is a different class of hardware.

Up until recently, most of such project were "open" in the sense that the list of parts and the PCB schematics where available.
It still wasn't something that could be easily replicated despite openness.
(You would need to be able to source the chips, to produce the PCBs, to surface mount everything needed on it, etc. getting the first boot loading firmware flashed required special debug boards, etc.)

More recent project such as this Raspberry Pi phone, basically require easy to obtain and manipulate parts.

Spent an afternoon ordering stuff online, and then your young nephew should be able to assemble it: no SMD-soldering skill required, only being able to plug daughter boards into headers.