Why doesn't the .serialize() method work on iPhone?

Question

JavaScript

There is a certain form on the site, the data from which is sent using AJAX.
Form code:

<form id="uni-form-1" class="uni-form" action="unisender.php" method="post" target="_blank">
        <div class="uni-form__title">Заполните форму,<br> чтобы начать консультацию</div>
        <input type="text" id="uni-form__name" name="name" class="form-control" placeholder="Ваше имя" onkeyup="setCapitalLetter(this.value, this)" required="">
        <input type="email" id="uni-form__email" class="form-control" name="email" placeholder="Ваш email" required="">
        <button id="uni-form__send" name="send" class="btn btn-1 uni-form__send"><span>Начать сеанс!</span></button>
        <div class="success-message" style="display: none;" ></div>
        <div class="confidentiality uni-form__text"><span>Я гарантирую Вашу конфиденциальность. Эти данные нужны только для отправки Вам второй сесси Робота-психолога</span></div>
      </form>

JS:

$(function(Subscribe) {
  $('.uni-form').submit(function(e) {
    var $form = $(this);
    $.ajax({
      type: $form.attr('method'),
      url: $form.attr('action'),
      data: $form.serialize()
    }).success(function(){
      console.log('success');
    }).fail(function() {
      console.log('fail');
    });
    //отмена действия по умолчанию для кнопки submit
    e.preventDefault(); 
  });
});

Works everywhere except iPhone. Empirically found out that the problem is in the .serialize() method. The problem is solved if, instead of data: $form.serialize(), send data with the array data: {email: email, name: name}, having previously received the contents of the fields, and writing them to variables.
But I would like to understand why the .serialize() method does not work.