The checkmark appears only in the translation direction EN > * and I understand her harm (he is suffering), then it just hurts when you need back translation * > EN, but EN > *, and the entered text is wasted. Therefore, it is possible to bookmark to add a reference for example
translate.google.ru/#en/ru|and then the transition will be immediately exposed to the direction of the en > ru and useless tick will not :)
\r
If you have any other problems, it is possible to write a bookmarklet that will disable the checkbox.