And also, it is true that it's harder to hit higher HRs in some sports vs others.

Swimming gets your HR up the "lowest", cycling is in the middle, running is near the highest, and x-country skiing getes your HR up the fastest. Of course, all the HR stuff is useless if your muscles and tendons aren't adapted to the sport. You can have a monster VO2 and amazingly low HR, but get toasted in an endurance sport you aren't good at because your muscles aren't specifically primed for it. (A la cyclists trying to learn to swim for triathlons or Lance running the marathon.)