That happens because injuries have hidden decimals, not because they are estimates. I don't see why it's necessary to make an erroneous assumption, when the mechanics of injury healing are known pretty well.
I think our difference here is a difference of language.
I completely understand that injury healing time is a precise number. I am not arguing that this is not the case.
What I am saying is that we, as end users, do not KNOW the precise number. We are not given the decimal... so a 3 week injury could be 21 days... or 24 days or even 27 days.
As such, from an end user perspective, you can call the 3 weeks shown to us as a "rough estimate" as, as you have stated, it may be 3 weeks or nearly 4 weeks.
We are in disagreement about a phrase, not about how the engine works.