So... correct me if you got more up to date information but I've always been under the impression that:
Diastolic pressure is more of an indicator of overall fluid balance, with a low diastolic indicating volume depletion such as dehydration or blood loss, and a high diastolic indicating fluid overload, from endocrine kidney or cardiac pathology usually.
Whereas pulse pressure is more of an indicator of sympathetic tone, whether that's drug induced or from a physiological state or possibly as a compensatory mechanism.
Thus an otherwise healthy person could be volume depleted and have a low diastolic while still having a normal systolic because their body compensates by increasing sympathetic tone and thus increasing cardiac output.
I've also been under the impression that diastolic pressure is a stronger prognostic indicator than systolic or pulse pressure. Did you learn something different in your Google search?
Now granted my knowledge base is much more geared towards emergency medicine and thus acute states rather than chronic, so the pathophysiology of ongoing hypertension isn't as familiar to me as say, the physiological responses to trauma.