> What? That seems totally backwards. Don't spend money you don't have, which mean using debit. Credit is useful for the single use case of buying a house.

Using credit in this sense means using a credit card, not necessarily running up a debt in anything other than a nominal sense. Using a credit card and paying off your balance in full every month (so that no fees are assessed) is way better for later loanworthiness and similar credit-based evaluations than using a debit card.