The goal of an emergency fund is to be available for an eventual emergency. If you lose your job and need to live on saved up money for a few months, you might be forced to sell stock at the wrong time, losing capital. There is a middle ground where you invest that money in a low-risk investment product that will grow with time, without the volatility of the stock market.
To be fair, 6 month is a lot, and most likely not the first goal someone should have when it comes to personal finance starting from zero.

This is actually inspiring. Not sure most poeple could afford installations like in the second video though. And the guy in the first video did have a point; it would be hard to share this lifestyle with someone else, or even just to invite friends at home up to a certain point.