The responses attacking your point here seem to be operating under the assumption that the manager, and the OP's peers, don't recognize when someone is obfuscating their effort and/or results. People notice.

"Bullshitting" is defined as "be misleading or deceptive" and the cost of this is borne not only by "management" (who presumably is in this constant mode of misleading or deceiving you), but by your peers who are dependent on you, or who are waiting for you to deliver.

As someone who gets burned out from time to time, I totally get it. It's tempting. I don't know the best general solution, especially if you're in an environment of distrust (rather than what superplussed assumes). But maybe explore some other paths? If you're in a job where in order to function, you have to deceive your management AND your peers, maybe you'd be happier in a different situation or company or role. To the OP: are you trapped in your situation? (It may very well be that you are, for instance, due to market conditions or visa situation, which sheds some light on why you're opting for deception.)