The reason for this perception is because, if you claim it would take 4X, but you finish it in 1X, or 2X, or 3X, you can just pretend to be still working on BS

The reason for this perception is because, if you claim it would take 4X, but you finish it in 1X, or 2X, or 3X, you can just pretend to be still working on BS things, and then viola you're finished at 4X. Otherwise, if you claim it when you actually finished, which was earlier then estimated, you look like a rockstar for having finished early.