This is, categorically, not "terrible advice". There might be better things to do, sure. The author is clearly suggesting that it's just a starting point. He/she is clearly not stating that this is a plan for life, or a plan for a large amount of money, or anything of the sort.

For many people, just getting started is a huge barrier. Index fund? What is that? Mutual fund? What is that? Buying a dozen stocks in some companies you've heard of can at least get you interested. You've got skin in the game. Now you are motivated to learn. The idea that you have to learn a whole load about it first just doesn't make sense. People are busy, it's tough to get the motivation to learn. Skin in the game is a great way to start.