This all makes excellent sense. Climbing I'm careful about eating too much in advance, my stomach tends to "discuss matters" with my harness if it's full...
If I'm climbing hard (indoors, 2 hrs) I'll ALWAYS get hungry after an hour or so no matter what, then it's off to the reception to see if they have any bananas, or scrounge a sandwich off my climbing buddies... And I drink a lot too.

Biking I rarely get hungry. I eat well in advance, and will maybe eat one energy bar in the course of two or three hours. I don't get very thirsty either, which has surprised me because I sure get all het up and sweaty I get thirsty afterwards though, and will eat anything not nailed down.

But I think maybe very aerobic exercise suppresses appetite while you're doing it. Climbing is more high-intensity but feels "less strenuous" since there are a lot of down-periods interspersed. And it seems that my body can tell the difference just fine