Currently the text stage always fetches the document: https://github.com/mongodb/mongo/blob/r2.8.0-rc1/src/mongo/db/exec/text.cpp#L291.

This can be a significant amount of wasted work if just doing a count of documents matching a query. A WT test runs 4x faster with that line commented out (obviously not a real solution but a reasonable model for how one would perform).