I'm confused too. The parts are high quality and scream "in-house" and surely not the product of contract engineers or contract machinist work. But I don't think DJI has machinists or factories in-house? I would assume they are just the product designers but I guess it's probably some kind of unique workflow due to Shenzen.

I just anecdotally see that in the USA, the required iterative design process is too cost-prohibitive for injection molding, and likely the same for every other trade. So multiply number of trades (designer, CAD drafter, machinist, electrical engineer, software engineer, injection molder, assembler, etc.) multiplied by the number of experimental iterative processes required to build an institutional knowledgebase... it's cost-prohibited.