It's true that "backdoor" is sometimes used as you defined. I feel that some usage, like this article, implies a deliberate backdoor. But you're right that it's

It's true that "backdoor" is sometimes used as you defined. I feel that some usage, like this article, implies a deliberate backdoor. But you're right that it's an implication and not an explicit statement. One reason that I feel this implication here is that an 'unintentional' backdoor vulnerability can be exploited by any attacker, but the article focuses on this backdoor's exploitability by Huawei, and by implication their untrustworthiness.