On PHB p182:
When you make a high jump, you leap into the air a number of feet equal to 3 + your Strength modifier if you move at least 10 feet on foot immediately before the jump. When you make a standing high jump, you can jump only half that distance. Either way, each foot you clear on the jump costs a foot of movement. In some circumstances. your DM might allow you to make a Strength (Athletics) check to jump higher than you normally can.
I understand the RAW, but my question is, what does that mean really? What portion of the jumper's body is clearing the obstacle? Do the rules mean that a halfling of average strength with a runup can jump up onto a table and land on their feet, then keep going? Or does it mean only the center of the halflings body is clearing the obstacle? Or maybe they are doing the olympic style flop high jump (which no-not really but is funny to consider)?
The idea that it is the height of your feet off the ground is supported by this portion of the jump rules:
You can extend your arms half your height above yourself during the jump. Thus, you can reach above you a distance equal to the height of the jump plus 1 1/2 times your height.
If it is the height of your feet off the ground, then a person of average strength (36") should be an NBA player. And a person with 18 strength is in the superhuman range (72" vs. the record for a running vertical jump in the NBA of 46"). At the other end of the spectrum, a 6'8" human with a 20 strength and a decent Athletics roll can jump up and grab the top of a 20 foot wall. Or, you know, just jump up and stand on the rim. Just like the gnome with a 20 strength can.
Are the jumping rules under the High Jump section really describing a running vertical leap wherein your feat clear the height listed in the jumping rules?