PPF is generally a thicker film, usually made from urethane. It has self healing properties that allow it to take abuse like rocks or scratches from other things. This film applies very differently from a wrap film and requires different techniques to apply properly.
A cast laminate is generally made from cast vinyl (though some other materials are used now) and is designed to provide UV and abrasion resistance to a print. It also adds dimensional stability to a print, which makes applying the print easier in most cases.
I wouldn't call them interchangeable even though they appear at first glance to do the same job.
Good l