I would refer you to the various resources on what each test is measuring. A DVD player can balk at a disc for any number of reasons, high PI/PO is one of them. The underlying cause is often that the player simply does not like that particular media type or format. High jitter can bother some players, as can relatively low PI/PO levels if the player does not like the media type. We have seen very small increases in PI/PO affect some players.
The bottom line is always to try different media, or a different burn speed. And often, the shortest route is to replace a balky player.
But as you become familiar with what your player will and will not tolerate, you can use the tests to predict success.
Based on experience with CDR's, it might be assumed that DVD's with high PI or PO rates may be more likely to degrade over time, so there's another reason to test. Demonstrating a progressively increasing error rate on a disc over a span of weeks or months is surely a predictor of impending failure.