Which is why I was careful to qualify that the problem was not with the person who does not know modern tech, but with the person who does. I was careful to speak in retrospect - that the teaching should have happened long ago, since it cannot and should not be done overnight.
Black money feeds into the real economy - possibly. But usually it has a very bad kind of "feeding". Investment priorities get distorted. Inflationary pressures on essentials, especially middle-class housing, that most primal of needs.
The question that needs to be answered is, WHERE is this "investment" going? Land, gold, super-luxury goods (to some extent), and so on. Not to mention, criminality and the underworld, election "funding" (read "distribution"), etc.
If you agree that bank deposits will increase as a result of all this, there's your answer. Investment and lending will find its way to the right sectors and projects, through the right channels. Ergo, GDP increase.
Speaking of bank NPAs which you referred to in your other post. It is no coincidence that the largest NPAs are with the PSBs. That's where political and other extraneous pressure comes into play. Why do PSBs show highest NPAs consistently? Sub-optimal decision making occurs only due to external pressures. Banks know pretty well what to do and what not to. So yes, lending does happen to the most productive, in the absence of external influencing factors.