Everyone lies, all the time. even when they think they're not lying they often are.
I don’t count it as lying unless there is intent behind it. But it is certainly true that many people’s deeply held beliefs are not as true as they think they are, myself included obviously. The more experienced you get, the fewer absolute truths there are.
Lying in engineering means saying anything that's not true with any certainty. I wouldn't hold it against someone, but I would ask them to think carefully before speaking, to make sure what they said is true, as it can lead meetings to decide the wrong actions if nobody present happens to be able to contradict it.
Outside of engineering, all the same outcomes can occur, but proving the truth is much more difficult. And thus, while it may still technically be lying, it is impossible to tell and unfair to call someone on it.