Under normal circumstances site review should be based on site quality and not how high PR is but some directory owners for reasons best know to them insist your site has a minimum pr to be included in their directory.
The one that make sense to me is to ask that a site has a minimum of PR1 as this will help you when reviwing the site to know that the site has not been banned in Google as you do not want to list sites banned by google.
Other directory owners ask for a minimum of PR3 or higher, in my openion this is the same thing as asking at you place a red cabbage on you monitor when submitting your site to my directory
