HI Homer,
I have tried the steps listed to recreate the issue and what I have discovered is that the filters (although copied exactly) create different results as the situation posed to the filter are different between the two modules. SInce the structure of the two modules is different (the hierarchy of the folders and what is presented) the conditions presented to the filter are in essence different for each module. The filter condition built on the hierarchy of the Test Plan module creates a different filtering condition on the Requirements module as the hierarchy that exists within it is different.
I hope this helps to answer your question.