Actually, it's both. Parent is arguing a consequentialist ethical framework - public health experts have a primary duty of care to the population, and their actions should promote this goal.

Your position of "you won't be trusted if everything coming out of your mouth is a lie" is fully compatible with this framework.

Considering the other person's mental model and incorporating their terminology when communicating with them, even when they're a bit wrong, isn't "lying" - it's basic empathy.