There are two characters ي and ی which are mostly treated the same in Persian typing (they are Persian character of YA).
As far as I know the correct one according to Persian keyboard is ي, but in all tests of this site ی is used (which is typed by SHIFT+X on my keyboard).
These must be some way so the site treat both characters the same.
Another thing, in regular typing and writing the Persian َ (SHIFT + A), ُ (SHIFT + S) and ِ (SHIFT + D) are not written. but in some of test words such as خُرد they are used, which shall be removed.