Isn't that situation covered in the original description? They said that marking squares that must be empty is fair game. The only thing not permitted is forced

Isn't that situation covered in the original description? They said that marking squares that must be empty is fair game. The only thing not permitted is forced backtracking. I don't think it's a bug in the javascript either, it seems intentional that it only fills in the x's automatically if you've filled in the squares for that row/column.