Django JSONField values aren't returned as a correct JSON-format in template when extracted using javascript

I have a model like

class UserGroup(models.Model):
    owner = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, unique=False, related_name="group_owner")
    name = models.CharField(max_length=128)
    group_users = models.JSONField(models.EmailField(), default=list, blank=True)

    def get_absolute_url(self):
        return reverse("user_group_instance", kwargs={"pk": self.pk})

now, in my in another app I filter for a list of UserGroup instances for the given user, and I parse that query-set to a ModelMultipleChoiceField.

That works fine and such, the issue is that I want to extract the group_users in the template and add them to an array, using java-script, thus I have create a div which stores the (I would assume) json-array in the data-members attribute

<div id="group-modal">
        {% for group in form.groups.field.queryset %}
            <label>
                <input type="checkbox" class="group-checkbox" value="{{ group.id }}" data-members="{{ group.group_users|safe }}">
                {{ group.name }}
            </label>
            <br>
        {% endfor %}

</div>

now, when I in javascript get the data from the data-members the returned string is not a json-object e.g it is "['hello@world', 'foo@bar']".

The javascript is (simplified)

document.getElementById("save-groups").addEventListener("click", function() {
            let selectedPeople = [];
            document.querySelectorAll(".group-checkbox:checked").forEach(checkbox => {
                let members = JSON.parse(checkbox.getAttribute("data-members"));
                selectedPeople = [...new Set([...selectedPeople, ...members])]; 
            });

and the JSON.parse fails. I simply cannot wrap my head around why; I don't do any manually serialization of the json-data thus I let django do that stuff.

I could work around it by do some regex replacement, but I rather figure out what the issue is

import json

class CustomDecoder(json.JSONDecoder):
    def decode(self, obj):
        return json.dumps(super().decode(obj))
    

class Order(models.Model):
    sku_id = models.CharField(max_length=10)
    group_users = models.JSONField(decoder=CustomDecoder, blank=True)