Is labelling a checkbox as mandatory redundant?

Yes, it is redundant.

1. Can a checkbox be mandatory?
2. How do I make a checkbox label mandatory in Servicenow?
3. How to make multiple checkbox mandatory in ServiceNow?

Can a checkbox be mandatory?

The required property sets or returns whether a checkbox must be checked before submitting a form. This property reflects the HTML required attribute.

How do I make a checkbox label mandatory in Servicenow?

To make a label mandatory above checkboxes you need to first add the label, choose no other setting. Then add your checkboxes with an order to where they'd appear next to each other right under the label variable.

How to make multiple checkbox mandatory in ServiceNow?

On the form we cannot make group of checkboxes mandatory. However, you can use on submit client script or Insert/update business rule to allow/restrict submission if all of the checkboxes are not checked and display the error message to the users. Hope that helps!