I can only speak for Calvary but I too have found names that have no markers. You also have to account for errors in the written records. When I first got the list of people in my Dougherty plot from the Calvary office there was a "James Dougherty" (listed on line this way also). Drove me crazy until I realized by matching death dates that is was "Jane", not James.

I think I have found my Dougherty family at St. Mary's online. When I confirm this and get a chance to make a trip there I am very curious to see if there are any markers.

Another thing I noticed was online for most of the older burials it says death date unknown. But at least at Calvary they have the dates in their records. I think the issue is the burial date is in the office records instead of the death date which is why death date is coded as unknown.

I believe "Web Cemeteries" is the company that created the database, I know for other cemeteries they code this way. You can view the other cemeteries from their site:
http://webcemeteries.com/
Click on "Search Cemeteries" at the top.
FYI--for most of the cemeteries if you click on "visit web page" it takes you to the cemeteries page, although that is not the case for all the CCAPgh ones.
Margie