Can a mock heroic epic mean the same as a serious heroic epic?
I think so. Throughout history, mockery and satire have been successful at providing context and meaning. Gulliver's Travels comes to mind as an example of a satire of faux-historical proportions which imparting meaning on its audience.
A serious heroic epic is much more likely to be easily recognized as meaningful to its audience, as satire often does not resonate with all people.
The Rape of the Lock and the Canterbury Tales also could fall into the mock epic category while being meaningful titles.