And it isn't a radar system
Well, I guess that depends how you define 'radar'. I would consider it to be one. At a most basic definition it uses radio waves to detect range and direction, even though the later isn't particularly accurate or vital.
OK, it doesn't have a rotating antenna, but neither do phased arrays.
OK, it relies on the cooperation of the target, in the form of a transponders, but so do most aspects of ATC radar use. That just makes it a secondary radar rather than a primary.
Going to have to disagree with you there Barry.
CPB