You can also use the ikkyo curve as a purely physical concept, though. Generally speaking, many different techniques involve displacing uke along a line that appears in its purest form in ikkyo. So checking to see if you're using that curve is a quick way to see if the geometry of your technique is correct.
Yes, for me, it was much more of a technical tip that helped me, as a nikyu level guy, move from usually not being able to make ikkyo work on an uncooperative partner, to suddenly being able to make ikkyo work almost all of the time unless my partner was particularly solid.
Later on I found it fit in with a lot of stuff Saotome Sensei was saying about the proprioceptive "energy body" that extends passed the skin.