If they do it may a sign of a directory in violation of Googles terms of service. Directories that use automation to update page rank statistics for their listings may be violating Googles terms of service. That may be something to note when you are determining the quality of said directory you are submitting to. Check here - go to Quality guidelines - basic principles and read bullet point 4 - there you will see this... So one could take from that - sites which use unauthorized programs to automate and check page rank or send programmatic queries to Google may be violating their guidelines. Just putting that out there as food for thought.
We have taken measures to prevent listings by Pagerank & also disabled the module. It doesn't make sense to prefer pagerank rather than quality and also trouble Google with unnecessary pings.