I doubt that there is really good data showing a stress EKG is better (makes you live longer or less likely to have MI) for athletic bike riders-than just a history-
"do you get chest pain while riding-at what HR"
On the bight side it is cheaper safer less invasive than a catheterization.

If you have EKG changes under load/exercise it means you have a fixed blockage of an artery.
Sometimes these fixed blockages will cause chest pain-but chest pain isn't always chest pain-especially in women-unclear why.

It DOESN'T mean you will have an MI- old fixed blocks are usually stable-don't suddenly break/lift up-clot off>MI-they can but usually don't
New "lesser obstructions" are more likely to break-lift-clot obstruct>MI
The stress EKG can't tell old plague from new plague-a catheterization "Might" be able to tell older smooth plague from newer less smooth plague.

In any case-don't worry.What you doc saw-extremely common as people age.
You are exercising- have good BP- decent lipids levels- eat right- and have plenty of cardiac capacity -
if you ever have chest or upper digestive pain pressure burning arm pain odd feeling something isn't "right"- head to ER- heart burn can be MI
Now not a bad idea to take 81mg aspirin a day-small bleed risk-but decrease MI risk...so
Yeah your heart is plenty good-this is strictly hunting for potential problems that would be relatively easily "fixed" at your leisure.
Luck
Charlie