I need to add a new group in the Sales category. I have seen that in the "sales_team" module the groups are like this:

<record id="base.module_category_sales_sales" model="ir.module.category">
    <field name="description">Helps you handle your quotations, sale orders and invoicing.</field>
    <field name="sequence">1</field>
</record>

<record id="group_sale_salesman" model="res.groups">
    <field name="name">User: Own Documents Only</field>
    <field name="category_id" ref="base.module_category_sales_sales"/>
    <field name="implied_ids" eval="[(4, ref('base.group_user'))]"/>
    <field name="comment">the user will have access to his own data in the sales application.</field>
</record>

<record id="group_sale_salesman_all_leads" model="res.groups">
    <field name="name">User: All Documents</field>
    <field name="category_id" ref="base.module_category_sales_sales"/>
    <field name="implied_ids" eval="[(4, ref('group_sale_salesman'))]"/>
    <field name="comment">the user will have access to all records of everyone in the sales application.</field>
</record>

<record id="group_sale_manager" model="res.groups">
    <field name="name">Administrator</field>
    <field name="comment">the user will have an access to the sales configuration as well as statistic reports.</field>
    <field name="category_id" ref="base.module_category_sales_sales"/>
    <field name="implied_ids" eval="[(4, ref('group_sale_salesman_all_leads')),
                (4, ref('mail.group_mail_template_editor'))]"/>
    <field name="users" eval="[(4, ref('base.user_root')), (4, ref('base.user_admin'))]"/>
</record>

So in my custom module I've tried adding the group to the Sales category like this:

<record id="user_channel" model="res.groups">
        <field name="name">User without channel</field>
        <field name="category_id" ref="base.module_category_sales_sales"/>
        <field name="implied_ids" eval="[(4, ref('sales_team.group_sale_salesman'))]"/>
        <field name="comment">User unable to view sales records with channel</field>
</record>

I see that my group is added to the category, but now the fields are no longer selectable, they are now all checkboxes. Is there a way I can add a group without losing the selection type so that I can only choose one group?