it may be obvious to you what he talking about, but your miss using the same terms.
FITNESS to do what exactly, cardio and aerobics though to some degree related and you get a benefit to both from either exercise, though in different amounts, are not the same thing and have contra indicators
if your doing ( extended)aerobics and your heart starts beating like a drum, thats not because your working your heart its because you've run out of oxygen, and your heart has gone into overdrive, thats not a good place to be, stop and let your heart normalise, keep going and you will a best calapse as the oxygen to the brain is cut off. you know your aerobic capacity has improved when your heart barely moves
cardio on the other hand is blasting your heart up to close to max for a short period of time, if your breathing gets highly elevated it shows you heart isn't what it should be as its not pumping the required the blood and the oxygen it carries
i had a conversation with a guy my age on a cycling forum, who was proudly telling me his cycling blasted his heart up to 200 for an extended period, he thought this meant he was fit, i said no mate that just shows how poor your aerobic capacity is, keep doing that and you will die
Oh jobo, cannot you not see that you are arguing against yourself?
You said: "if your doing ( extended)aerobics and your heart starts beating like a drum, thats not because your working your heart its because you've run out of oxygen"
You said: "cardio on the other hand is blasting your heart up to close to max for a short period of time, if your breathing gets highly elevated it shows you heart isn't what it should be as its not pumping the required the blood and the oxygen it carries"
There is a notable "chicken or the egg" situation here.
BOTH exercises require blood to be adequately carried which in turn carries oxygen to the body; assuming there is adequate oxygen there.
Frankly, I wish it was this simple. There are many other things as play here, such as lung capacity, vascular health, and muscle makeup. Then you get into the endless list of things like BMI, genetics, mentality, on and on.
To me, the answer is, if a person has the time and 'want to' to exercise 10 hours/week, AND it is quality time spent (not just conversing as the gym) they should do it. It certainly lends itself to being a lifestyle and not just a New Years resolution that is going to last for a couple of months.
If time is at a premium, the a person has to figure out how/what exercise they can fit in to their schedule. Part of the problem with this scenario is that Most people cannot jump right into the exercise regimen you describe.
It takes a little time but a committed person will figure what they need to work on the most; strength, cardio, flexibility, etc... Then they can figure out what best to do with the time they have available.
And Yes, the terms cardio and aerobics are interchangeable in terms of exercise.