I stand to be corrected though , but I do not support the idea of telling someone that they should invest what they can afford to loose , it makes it sound like crypto is strictly gambling so the person should only gamble with what they can afford to lose..
Though telling someone to invest only what they can afford to lose can also be another way of telling them that the crypto market cannot always be predicted accurately 100% of the time.. .But some newbies might misinterprete the phrase "Invest only what you can afford to lose"..
So whenever I want to introduce anyone into crypto trading , what I tell them is that they should not see crypto trading as a get rich quick scheme...Rather they should see it as a form of investment which can give them good returns on their investment for future purposes...Then I make them to understand why they need to understand the market itself and also the importance of risk management too..