If Apple Maps gives you bad information, you usually can correct the wrong turn you take without too much difficulty.
If glucose monitoring gives you bad information, you could easily lose body parts, die, or other bad outcomes (In the last 10 years, one of my friends died, after apparently having lost several toes in an earlier episode. Another friend was rescued by the police after driving on the highway for several hours in a disoriented state. Both of them were medical professionals and presumably using best practices in their monitoring).
So you've just proven that medical technology in general suffers from problems of edge conditions and individual variability, but you expect that Apple needs to create a literally perfect product.
Not literally perfect, but with the awareness that the stakes are considerably higher than generally with their products, both from an ethical and a product liability point of view (Apple's vast resources could prove problematic on the latter aspect, as they would represent a particularly deep pocketed target for potential litigation).
Apple Maps has been working entirely fine for me.
For this glucose monitoring the early product that Apple ships will almost certainly be grossly inferior to the product 10-20 years later.
I don't understand why this is a problem.