A negotiation tactic: getting an actual job offer in hand for your salary + X, and then indicating to your manager that you have an offer for $S+X and that you would like to stay where you are if they could match.
Lying: not getting a job offer, but tell your manager you did.
Also lying: getting a job offer for $S, or $S+0.1X, but telling your manager you got an offer for $S+X.
"Lies" and "negotiation tactics" are overlapping sets.
There are negotiation tactics that are not lies, and lies that are not negotiation tactics, but just as surely, there are lies that are negotiation tactics.
> Lying: not getting a job offer, but tell your manager you did.
Sure, that's a lie. And if you tell your manager this as part of a stratagem to get a better compensation deal in your current job, its also a negotiation strategy.
It may be an unethical negotiation strategy, but it is certainly a negotiation strategy.