Sorry for the late reply, I got tied up and am just now getting back to the topic. To try to explain why the type of leave matters, I will use an analogy.
Let’s say that you are a youngster and your parents told you in January that they put aside $1000 for the year for you for your entertainment expenses (movies, camps, sporting events, etc.). But there is a catch. It is in two accounts. The first contains $800 and can be used as long as you give your parents a three-day notice to help prepare for and make arrangements to get you to where you want to go. Let’s call it the ‘planned’ money. The other $200 is in a pre-paid debit card that can be used any time with a two-hour notice, and we’ll call it ‘mad’ money.
So, in March you ask your parents if you can go to a concert in May that will cost $75. You’d like that money to come from the ‘planned’ account since you’re giving plenty of notice. Your parents say that you can go but only if you use the ‘mad’ money. That wasn’t the deal, right? You followed the rules and gave a notice, but the money still has to come from the ‘mad’ account? This would limit the amount of participation in unexpected entertainment opportunities that could possibly come up.
In my OP, vacation time is ‘planned’ leave and PTO leave is ‘mad’ leave. If an employee is able to give an acceptable notice, he should be able to use vacation leave and hold on to the PTO leave in case he needs it for unexpected events. Our employer was OK with him taking off that particular day, they just wanted him to use up his ‘mad’ leave even though he gave the required advance notice to use the 'planned' leave.

