I know what you're thinking, that describes a LUT (lookup table). Yes, you would be correct, a LUT is an actual profession in the USA.
Grocery bagging, likewise, is hardly a bullshit job. I shop at whole foods precisely so I don’t have to bag my own groceries. (And a good bagger can do it far better than I can.)
Are they just faster?
There is a tremendous amount of tech in medicine and considerable investment at larger healthcare systems. If medical coding were such a simple automateable problem it would have been done (I mean it’s freaking billing... absolutely the strongest and direct financial incentives to solve).
The first mistake/flaw you’re making is that the healthcare provider uses codes. That is most often not the case. Even if they do, it gets more complicated with submitting claims.
There are plenty of LUTs in healthcare that are managed by the EMR, billing ain’t one.
This profession exists only in the US. What are the other modern healthcare systems doing so they don’t need a coder? I’ll leave that for you to discover.
[1] https://www.bls.gov/opub/reports/minimum-wage/2017/home.htm