> Gaslighting is a form of psychological manipulation in which a person or a group covertly sows seeds of doubt in a targeted individual or group, making them question their own memory, perception, or judgment
Other than the goal being "seeds of doubt", manipulating someone into thinking something untrue is really not far from gaslighting.
> The goal of gaslighting is to gradually undermine the victim's confidence in their own ability to distinguish truth from falsehood, right from wrong, or reality from delusion, thereby rendering the individual or group pathologically dependent on the gaslighter for their thinking and feelings.
Is the described behaviour manipulative? Sure. But compared to everything I know of gaslighting and the intents behind it I don't see much similarity, not with more context than a single sentence at least. Did the manager do it to help people's careers? Did he try to lure them into a satanic cult? There's a wide range of unknowns.