Motors are no monolith, and the various scaling factors WRT bearing quality and air gap (among other construction tolerance issues) mean the smaller the motor i

Motors are no monolith, and the various scaling factors WRT bearing quality and air gap (among other construction tolerance issues) mean the smaller the motor is, generally the less efficient it is. What is motor efficiency is very much a "how long is a piece of string?" question. All engineering is about tradeoffs and if the kid is replacing air gap with "something", that efficiency has to be balanced against better bearings vs better mfgr tolerances etc. Its still a valid tool in the collection of tradeoffs; but its unlikely to match the boosterism tone of the article as being "the solution to all our problems". The problem with boosterism is not that its positive or criticism is good or complaining that contest he was in, is mostly a contest of parental income and willingness to spend, but the problem with boosterism is it can completely overshadow any actual science or engineering. The kid probably DID do something cool and interesting, but it's buried under the boosterism and exhilarating claims of world changing etc. Its a valid criticism because this kind of popular coverage gives the false impression that actual science journal articles or EE component datasheets should consist of 99% boosterism with perhaps 1% content. From a journalistic perspective its worthy of criticism in the sense of this is NOT science and engineering journalism, its just a puff piece full of glory and sparkles. From an educational perspective its worthy of criticism in that the tone of the article implies kids should not go into STEM fields unless their parents are rich and easy spenders, which ironically would be a better match for a non-financially rewarding liberal arts degree; I assure you that a kid can grow up to be an excellent EE even if his parents can't afford a 3d-printer.