There is not enough depth of field from any regional ironman to know what the age related degradation is because there is not enough of the field optimally trained to execute at the distance providing a sample of what happens to humans over the distance at hand based on age. Largely the course does not make a difference. If you put the world’s field on every IM globally you’d arrive at roughly the same degradation. Maybe cooler flatter courses you may get less degradation for the 65+ but below that age group, I doubt you will get much of a difference over courses. My feeling is that the Depth of field matters more to statistically determine what the age related degradation is for all humans than the course does and for 70.3 its been averaged out now over St. George, Lahti, Taupo (can’t remember if Nice 2019 was included).