Hello

please have a look at this post. 

As I underdstand from that post, there is no way of referring to a Data page by passing keys directly like we would call a Data Page using parameters.

Is there any particular reason for this?

Unfortunately i dont have idea that what is the reason. Lets see what other folks in the forum has to say.

Keyed data pages require auto-populated properties.

You can then set the case property values that the auto-populated property uses to load the appropriate data page and key into it.

There is a good PDN article explaining this design pattern: https://pdn.pega.com/instantly-access-embedded-pages-list-structure-data-page