Problem:

When I am creating or editing a record, and duplicate records are detected, I can still save the record even though I did not tick the ‘Disable Duplicate Check’ checkbox.

Answer:

from DC version 3.362 onward, the ‘Disable Duplicate Check’ checkbox does not need to be shown on the page layout anymore in order to override the blocking of saving records that have duplicates. Instead, anyone with at least Read access to the checkbox can now always override blocking. 

If you still have the checkbox displayed on the page layout, it will now behave as if it is always ticked for those that can view it. Read more in DC Entry.