I don't think I know anybody who facilitates cooperative learning in the classroom who believe students should be evaluated that way even half of the time. Pairwork or group work is helpful because it gives students a chance to talk about why they chose the answers they did, and gives the students who take a little bit longer to catch onto the concepts a few more chances to get it before you come by to see what they know. A gallery walk early in an assignment gives students who are off track the opportunity to see other students doing what they are supposed to be doing, before they get even further off track.
I like to give students the opportunity to work in a group before I give them an individual graded assignment on the same topic/skill/process. Besides, research shows that cooperative learning, counterintuitively, encourages students to become independent learners.
Not always a problem for our gifted learners, of course, and many gifted adults look back on group work in school with a shudder. They use words like "exploitation". The role of cooperative learning with gifted students is a hugely controversial one.
Having been on a graduate admissions committee that unanimously turned down an applicant with solid test scores and grades on learning that nobody could work with the applicant, I insist on cooperative learning. But I also make sure that a cooperative group with a gifted student has at least one other member that *approaches* them in ability.