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It may be not directly but rather how soon you begin to see PR appearing, say from the sandbox.
Because PR that you see is not the instant PR that Google operates. It is rather past PR averaged over several month and Google seems decides when to show it taking into account the page quuality.
So if previouly you have a homepage of a PR4 and internal page of PR0 - in this update your internal pages could be showing a PR5 while the homepage remained at PR4 - this is only because the homepage PR has not been updated though - if it has been updated I would have thought it would be greater or equal to your internals.
If you are talking about the recent update then in the update thread it has been pretty clearly established that the lastest PR update only happened for pages which did not have PR.
Indeed this has been the case. However, I am experiencing a slight anomaly (which has been flickering on and off for the past few weeks) where the homepage has remained a PR5, while roughly 12 of 15 top level pages which had a PR of 4 for the last 2 years have gone up to 5. The homepage remained at 5.
Strange new PR behaviour - I reckon they're digging deep and doing a bit of the old spring cleaning.
WARNING - when you read that thread, you will see that this is not looking like a "regular" PR update. What you see now may not last all that long, and may not reflect the actual PR values currently in use behind the scenes.