How to Configure via data-* attributes

According to the documentation, I should be able to set some configuration via data-attributes on the select tag.

https://select2.org/configuration/data-attributes

In my code, I tried this:
<select id="customer_select_form_customer" name="customer_select_form[customer]" class="select2-ajax-enabled form-control" style="width: 500px" data-theme="bootstrap4" data-ajax--url="/customer/ajaxList" data-ajax--cache="true" data-select2-id="customer_select_form_customer" ></select>

I tried to initialize this with the following, but it does nothing:

// enable the customer ajax list
$('.select2-ajax-enabled').select2({});

I also tried to set the parameters, and have them override, but that didn’t work either:

    // enable the customer ajax list
    $('.select2-ajax-enabled').select2({
        theme: 'bootstrap4',
        minimumInputLength: 3,
        ajax: {
            url: '',
            dataType: 'json',
            cache: 'true'
        }
    });

Is there a configuration/setting that I’m missing to get the data attributes to work?
If I specify the whole config and pass it to select2, it works as expected.

I’m using jQuery v3.3.1 and Select2 4.0.6-rc.1

Following up because I figured out that this was not working because of a bug in 4.0.6.
I reverted to 4.0.5 and my code examples are working now.