Some of the space pundits are questioning NASA's mission as a pointless excuse to justify SLS/Orion, as there's no reason to send astronauts all the way to the moon merely to take a sample of an asteroid by hand. As the Mars rovers show, we can do a vast amount of science and manipulation without
a manned presence, especially in the case of a very small target where a human's speed and agility are hardly necessary.
In this case the mission profile seems more political than technical. Earlier in the asteroid program NASA was ignoring any asteroid candidates below about 500 meters as being unworthy of a visit. Those plans were aimed at sending a human deep-space mission to an asteroid in-situ, and nobody would spend a couple billion dollars to see an Orion fly for a month to pull up to a rock about the same size as an Orion.
Then they apparently ruled out such a mission for budget and schedule reasons, so the goal would have to be less ambitious. Capturing a much smaller asteroid (perhaps 5 meters diameter instead of 500) and bringing it closer to us fit the bill, and that makes it easier to get an Orion mission to it. But if they brought it into Earth orbit (which wouldn't be an unworkable delta-V requirement) they could visit it with a Soyuz or Dragon on a Falcon v1.1, which doesn't justify building the SLS or the Orion. A remote sampling of the asteroid likewise fails to justify the manned spending.
This seems to be a case where the mission exists to justify the program and the mission requirements are written to justify the type of equipment we're building. It will probably fall by the wayside as soon as they find a better justification for the same equipment.
What they probably want to architect is having the Orion hook up with a manned asteroid processing facility in lunar orbit or L5, but that probably looked too expensive, long term, and easy to cancel.