When the value "JOINT" is entered in step 4 of 10 under Document Separation Profile "Separate on specific Zone OCR/ICR values and patterns" all variants of the word joint will separate. This includes joint, JOinT, and so on.
By default it will be case insensitive if you enter in a capital value to separate on. This means that if you have JOINT set it will match all variants of the physical value JOINT such as joint, Joint, JOiNT, and so on.
Without Match Case turned on you would have to use (?-i)JOINT. This will match JOINT and not potential variants like joint, Joint, JOiNT, and so on.