[broadwaylamb]

> Why would you instead keep your manager in the dark?

Because you're already providing enough value to justify your wage even with padded estimates and slacking off (otherwise your manager wouldn't have been happy to begin with). They just want to get more out of you via the expectation of "reasonable best effort".

In other words, your 50% effort was already good enough to provide the company the value it needed (was willing to pay for), but some managers feel entitled to 100% if you demonstrate that capacity to them. So just don't.

And the reality is that many places don't genuinely need people's best. What they actually need is "good enough", and that's already reflected in the wage via profitable business outcomes that role contributes to. Time and effort have nothing to do with it.