dupe: and sizedupe: find duplicates in the entire index, not the current results, so the results are not very meaningful when you combine these two search functions.
Think of dupe: and sizedupe: in Everything as:
duplicated file names in the entire index and duplicated sizes in the entire index.
finding duplicated names in a list of duplicated sizes (or duplicated sizes in a list of duplicates names) is a two pass search, which Everything is not designed to do.