By default when a work object is created then pyWorkPage is created into the clipboard to hold the information related to the Case. So i don't declaring your page name as pyWorkPage in Pages and Classes is the right approach to do. Is there any specific reason behind this usage?
In order to refer data from pyWorkPage (i.e...,data from case) in another rule which is in different class other than pyWorkPage (say,rule is in Assign-) i created pyWorkPage on Pages and classes tab. Though the functionality is working fine, i am not sure whether it is best practice to create pyWorkPage on pages and classes tab.
When you declare something in Pages & Classes tab, platform will not create any page. A declaration in Pages & Classes tab is used to validate the design time references of given page in sections, activities, etc. Page will be created by activity methods like Obj-Open, Page-New, etc.
If you're sure pyWorkPage will be your workpage always, I'd say there is no harm. Many a times, your work may take place on a different page but if you don't have that requirement, pyWorkPage can be used and referenced.