Just my opinion, but I feel like these kind of sports are unbalanced, because our muscles are mostly powerful for legs, of course rowing is still using legs, but not much more than arms
As mentioned you are wrong on this: rowing is mostly legs, some core muscle and then a little arm. As you don't have your full weight on your knees it is a good way to get started on working your legs when you're overweight.
As someone who rows an actual boat once or twice almost every other summer I just want to say that rowing is mostly upper body and arms, with little to no legwork.
Not a professional rower, just looked into form when I was using a rowing machine.