I'm going to attempt to respond again ... The last attempt didn't post because of a system glitch, so the response from me might come across twice.
If I'm reading your question correctly, I believe that you are misinterpreting the statute. "An employer must compensate a terminated employee in full on the day of termination" translates to any back wages must be paid to the employee upon point of termination. i.e., It can't be mailed.
Back wages do not include hours not worked on the date of termination. So, if the employee doesn't immediately pay you for accumulated hours when he/she terminates you -- there will be a problem facing the employer.
If the statute meant that the employer owed you for the entire day, they wouldn't be terminating you until the end of the day.
Further reading your post, if your employer is paying you by vacation pay, that's ludicrous to be paying out of vacation time. Vacation time isn't used to become terminated. I don't know the vacation pay law in your state. You might want to check with DOL.