Both datalist and combobox are restricted to what is in the DOM at the moment. Neither of them can understand misspellings or foreign variants if not already in the datalist, for example.
An autocomplete is typically written to understand variations and generally has a component that communicates with the server (or a service) to look for near matches, and address common typos or variants.
I did not experiment with dynamically-updating datalists, because in the end the code is still a datalist. Autocompletes can be coded using a variety of means, just as programmatically-associated lists (as in your example).
So, programmatically I think datalist and combobox are more closely aligned.
If explaining this to a non-technical person outside of your development workflow (such as a client), then any wording would work as long as you get enough detail in requirements analysis to understand which technical implementation is the best fit.
Does my decision tree make sense?