Version 2.1.26
I create a custom field that is a checkbox type, and it has multiple field values (e.g. xxx||yyy||zzz).
I make the field required, either in the edit field settings, or using the #REQ prefix in a template.
The field when used in a form then requires that ALL boxes are checked, or gives an error to the form user when they try to submit, indicating the boxes that are not checked must be checked to proceed.

Issue: common use case for a multiple checkbox field that is “required” is that at least one (or more is OK) boxes must be checked (e.g. “check all that apply” and similar use cases).

Suggested: “required” on multiple value checkbox field means “at least one box checked” and not “all boxes checked.”