Yes, you can call in sick and use PTO to apply to those days as well. Take note that this may still count as occurrences that you have missed. If you go over, then you will lose PTO points.
Regular PTO lets you take time off work for holidays, family time, or other personal activities. PTO is what you need when significant life events happen, so you can put your full focus on that without needing to fuss about work. You also have the option of transferring your PTO if you don't use it all in one year or redeeming it for cash.