You might not be correct in the whole contexts but I understand your point.
Investing with what you can affordable to loose dogo actually mean you should invest little with little amount. It's just a statement that have to remind you about the risks of the markets volatility and as a human whose expectations fails against your confident, there'll be a room for you to keeping going without a weigh down emotional and your striving to achieve your financial obligations.You can call it an adage or advice from experience users in the bitcoin market.
And to make it clearer, your investment approaches which may be determined by your capital or accumulating plans determines your incomes depending on when you want to opt out. So it's right to invest with any amoun as long it can be tolerated. The risks is always yours based on affordability.
This is the exact meaning of the long statement of
Invest the amount you can afford to lose.I think the OP misunderstood the statement and thought it is all about small scale investment; it is not about small or large scale investment, it is all about risk management; how can you manage your risk by not regretting any action you took in your investment since if it is a gain, you will take it alone.
Crypto market is volatile, that is why instead of making quick decision without thorough research one should be patient and keep accumulating money before they will learn about crypto and start investing in it. And it is also a statement to limit people who are willing to make quick money to avoid loans for bitcoin trading or investment, because the outcome might not be nice especially if it is about trading shit coins without experience.