Why is there an error with compare?

Question

Yii

Here is the model

class SignupForm extends Model
{
    public $email;
    public $password;
    public $password_copy;

    /**
     * @inheritdoc
     */
    public function rules()
    {
        return [
            [['type', 'email', 'password', 'password_copy'], 'required'],
            ['email', 'email'],
            ['email', 'unique', 'targetClass' => '\common\models\User', 'message' => 'Данный Email уже используется.'],
            ['type', 'integer'],
            ['password', 'string', 'min' => 6],
            ['password_copy', 'compare', 'compareAttribute' => 'password', 'message' => 'Пароли не совпадают','skipOnError' => true],
        ];
    }

I form the form in the widget

class UserModal extends Widget
{
    public function run()
    {
        $signup_form = new SignupForm();
        return $this->render('user-modal',[
            'signup_form'=>$signup_form,
        ]);
    }
}

here is the widget view

<?php $form = ActiveForm::begin(['action' => Url::to(['site/signup'])]); ?>
        <ul class="user__type">
            <?= $form->field($signup_form, 'type', ['template' => 'clean'])->radioList($signup_form->typeArr, [
                'item' => function($index, $label, $name, $checked, $value) {
                    $checked_attr = $checked ? 'checked="checked"' : '';
                    return '<li><label><input type="radio" name="'.$name.'" value="'.$value.'" '.$checked_attr.'>'.$label.'</label></li>';
                }
            ]) ?>
        </ul>
        <?= $form->field($signup_form, 'email')->textInput(['placeholder' => 'Электронная почта'])->label(false) ?>
        <?= $form->field($signup_form, 'password')->passwordInput(['placeholder' => 'Пароль'])->label(false) ?>
        <?= $form->field($signup_form, 'password_copy')->passwordInput(['placeholder' => 'Повторите пароль'])->label(false) ?>
<button class="button button_wide form--button is-disabled" onclick="fbq('track', 'Lead');" data-next-button>Зарегистрироваться</button>
       <?php ActiveForm::end(); ?>

but here is such nonsense
https://prnt.sc/k60ymj
the question is why.
And this is only with client validation.