That sounds wildly micro-managey. I often don't know how long something is going to take until I dig into it; sometimes I don't know how long something is going to take until I'm almost done. The ambiguity/fuzziness of points is a feature, not a bug.

If I'm going to be "held to account" based on my estimates, I will optimize for producing work that matches my (naive, uninformed, up-front) estimate, rather than producing the _right_ work. This will last for a few months, at which point I will realize I'm burned out, working inefficiently, and writing bad code, and I'll find a new job on a different team that doesn't treat its employees like train conductors.