No Koi Babies? Why Do I Only Get Goldfish Babies Every Year?

It turns out that "turnabout" is Fair Play isn't actually a "thing" for Koi and Goldfish.
"Wondering why my koi aren’t multiplying ..? My goldfish have NO problems. Any ideas??"
You're mentioning something that's echoed across the country - and here's the reason: Koi aren't big egg-eaters*. If they eat any of the eggs it's just lazy, even accidental. HOWEVER, goldfish are avid egg eaters. And they'll scour the bottom of the pond and the plants for caviar after a spawn. You: "Okay, so?" So what happens is; the Koi spawn and then the Goldfish eat all those Koi eggs (and new fry). Then the goldfish spawn, and greedily eat more than half of their own eggs. But, (and so) the vast majority of new young fish 'born-in-the-pond' are goldfish, year after year. How does this play in real life? Them: "I have so many koi to get rid of. Hundreds." Me: "Are you sure they're Koi?" Them: "Yes, I saw them spawning last Spring." Me: "Do you have any goldfish in there?" Them: "Yes a few." Me: "Then all those dozens of orange and brown yearlings are Goldfish. I'll show you when I get there." As a side note: My favorite fish "species" is the Koi Comet Hybrid "Mule" - as they are a fantastic 'mid-sized' Goldfish-ISH that seems indestructible. Anyone know why those fish are all sterile? More specifically is it chromosomes, or a physical limitation?
*Msg'd by a fellow with a bunch of Koi in a little 600 gallon vat said his Koi eat ALLL their own eggs. So, I'll stand corrected that if the fish are in competition for space and food, and there's nothing do do but swim in a tight circle, you aren't gonna have any eggs, lol.