There is a difference in legal status between CL and other kinds of leave, as far as public service is concerned. CL is considered to be duty, while other kinds of leave are not. Therefore, if an employee is on leave (other than CL) on the day of their increment, the date of the increment would be postponed until they join duty.
The same applies to intervening holidays. While availing CL, intervening holidays would not be counted as leave. On the other hand, when on other types of leave, intervening holidays would be counted as leave, and holidays could be prefixed/suffixed. Due to the difference in legal status, availing CL is not permissible in combination with other types of leave.