I see it differently. I use my PDI to list faults which I have made the customer aware, for example - CD player/AC etc not working, body damage. Customer complains a month later and this documents that he/she knew this and has signed as such.
Similarly, I state things like 2 keys, locking wheel nut etc becuase when they lose one I have proof it was there at point of sale.
Having said that, no car leaves me with any safety critical boxes unchecked as OK.
Both the customer and I get a dually signed copy of such.