That is a very big clue they know they are telling outright lies with the 600 number. First the marketing guys are being extreme dirt bags on these units. They used to be called av500 because that is what the homeplug standard is called they are based on. When the new standard called av2-600 came out they renamed the units av600. They did not even change the part number you can still find av500 units with the same part numbers from time to time. They wanted to make people think that they are the new units when they are not.
Testing on these units even in the same room is well under 100mbps. Like wifi these rates are some theoretical things that only exist in unrealistic setups that can only be achieved in a lab setup.