No.I think you get cashed out of annual because of pay scale/classification change. But as soon as you turn regular, you are advanced the pro-rated remainder of the calendar year annual leave.
When you have an aux route, your leave time appears on your pay stub in days, but you use them in hours. Your example of a 4-hour aux would use up half of an earned AL day when you take off, because a day equals 8 hours. When you go regular, no conversion is necessary because it's already in days. If you worked an aux route before going regular, you are probably carrying partial days of AL/SL that will stay with you until you retire because you don't take time off in hours anymore.When did it change to hrs rather than days?