This is very good info here and 100% true. It takes a stronger more efficient cardio system to intensely contract ones muscles than it does to walk or jog. But somehow almost everybody thinks that walking or jogging type activities are superior in stimulating the cardiovascular system. As is stated above, specific training will produce certain results which are not remotely required for good vibrant health. In other words one could make the argument that if intense weight training was better for the cardio system then why if I try to go out and run a mile or two is it so hard? All that means is you aren't good or used to running and will very quickly adapt by simply running and yes your ability to run farther more easily will improve but this is not indicative of a better cardiovascular system and does not equate to better health.
All this said, if one enjoys running, walking, swimming, cycling etc. then by all means do them. The point is that the REAL cardio conditioning comes from a properly performed intense weight training program.