You're misremembering, here's a quote courtesy of
DND Beyond:
Compare this to the encounter guidelines from 2e, courtesy of
Archives of Nethys:
Both games define their ultimate difficulty as having a risk of the party being defeated and requiring good tactics. Their penultimate levels both cite defeat and death as a real possibility. There are differences between the two games (2e isn't reliant on an attrition model, so its encounters are a little fiercer by themselves) but on a basic level they map pretty well in terms of stated expectation-- the main catch is that 2e is more expressive about what 'risks defeat' likely means in the 5e entry and what kind of party can take on its extreme encounter-- note the 'or' used at the end, extreme encounters are still ok if used rarely, even when the party has suffered some attrition.