I've been in the stock market so I know what you're saying. My point was that there's a difference between saving something which implies not putting it at risk of loss, and investing in something for gain which almost always implies risking loss. So, I think it really was a valid rule, in the original post, to hold savings apart from the two investment choices.
The Beyond Meat example is typical of IPOs. Everyone gets pumped about the new company, speculators buy in big which demand runs up the price, then they take the money and run. There's a reverse version when a company is dying, called the "dead cat bounce". Speculators will buy big into the falling price stock, again causing the price to rise. More people pile in, sensing a turn in the company fortunes, only to be left holding the bag when the speculators pull their money & gains out.
Short term stock investing is, as you describe, a form of gambling. There are many professionals in it & you pit yourself against them & Lady Luck. Long term, you have better chances & can rely on slow growth (often at lower risk) of either a company or of the market as a whole. That's why it's smart-ish to invest as early in your working life as possible. Longer time to let compounding of interest & dividends build some wealth.
