Yeah, fake it till you make it only applies to overcoming self doubt, and should not be used to dismiss glaring problems. It certaibly doesn’t work as a cure all for actual problems.
It can in rare cases work for happiness, but only if the reason is one that is just based on self doubt while things are actually going well.
Packing all tbose differently sized parts into a tiny form factor is very different from comparably spacious computer cases. Then the power usage handling, and wiring, not to mention heat dissipation.
Not impossible, but being modular like that would increase the cost because doing that costs more in the context of a cell phone form factor. Enough that doing several models will keep the price point where people can afford them.