Wear items are never covered upon acquistion, but are sometimes (not always) a requirement before a CPO is sold. Some dealers to meet the spec do the bare minimum, so you'll see some shoddy work in tire brands, or you wont see cheapo pad slaps etc.I feel more comfortable buying a cpo.
Not sure how it covers wear items since wear items are never covered.
A battery could fail at any time, breaks should be checked before sale
A lot of these concerns would be addressed in an indy PPI.