Faking it is really a bad model - the number of Steve Jobs "prepared to use sleight of hand to hide loading times" is vastly out numbered by expensive failed replacements.
The most defensible practice are at least inherently modular and could be stitched together - really the deception would be highly unnecessary
Early on in a project you need vision and innovation, "fake it 'till you make it".
Get a demo working, even if it only works 20% of the time or covers one use case poorly.
But at some point, along comes actual reality.