As a native speaker with a Polish wife we agree that both small and little should be expected. I will report as well.
Native speaker of English who wrote "expected," which I assume was a typo instead of "excepted," except what you meant was "accepted".... /o D:
Isn't "little" the same as "small" in English?
A bit unrelated question: what is the more commonly used form of Genitive plural for koszula, koszul or koszuli?
Well, "koszul" is the only one that is really correct. You may hear the second one, but it's wrong.
Thanks. Interesting that this online Polish dictionary lists koszuli as a correct option: http://sgjp.pl/leksemy/#10068/koszula But I guess it really is not used after all.
So koszula is both a shirt that you wear with a tie and suit and a t-shirt that you would wear with jeans?
A t-shirt is rather "koszulka". Or, in fact, "t-shirt".
why is "a small shirt" wrong?
It's not wrong, it's an accepted answer.