Here's the answer:

http://www.ncbi.nlm.nih.gov/pubmed/20827654

Thus changes in muscle coordination improved the pedalling effectiveness during the upstroke phase but would probably lead to impairment of the oxygen consumption. Therefore, training the pull up action could be of interest to optimize this muscle coordination associated with better pedalling effectiveness by additionally relieving hip or knee extensors during the downstroke.

But even the gobbledy-gook study you cite states:

However, an active pulling-up action on the pedal during upstroke increased the pedalling effectiveness, while reducing net mechanical efficiency.

I'm not sure I quite get the set up that was used for this "study" WTF is a "single pedal" a platform with no toe clip? How would you pull up? The abstracts are not a lot of help visualizing the test set up in this "study."

This study seems to come to a totally different conclusion.

http://www.ncbi.nlm.nih.gov/pubmed/17545890

When the participants were instructed to pull on the pedal during the upstroke, mechanical effectiveness was greater

My conclusion is that these studies are pretty poor simulations of actual performance during a ride. They are poorly conceived and totally unconvincing in their conclusions.