That’s it, your assumptions are more or less correct.
“char” type, stores its value on 8 bits and can store a value between 0-255, while “short”, the next smallest type, has 16 bits and can store a value between 0-65535.
In terms of storage, this change would make double the size of the “inventory” databases. They also would have to rewrite part of the code to use new types and reorganize part of the database.
So, resolving this “bug” would be pretty expensive and it will have near to zero improvement on QoL.
I hope my answer is useful, sorry for my awful english xD