If you try building a framework on Arrow, you are most likely going to start with thinking about types and how you munge everything you are doing into the Arrow types.
I.e. ask yourself: would I not able to start working if my type system didn't have a 16-bit integers? Why would I care in my design if the system had or hadn't 16-bit integers?
And, if you are honest, the answer to this: no, nobody cares. Plenty of important design decisions don't require this information at all. In fact, the sizes of integers may never even appear in your query system (eg. all you deal is are byte strings), and it would still work...