I guess until I try a fanny pack riding, I'll never really know, but from never having things on my back or hips riding, I suspect I won't like the weight and or movement that would be felt with moving around on the bike--movement that decades of riding has me used to the feel of nothing there....
guess I'll just have to grab the fanny pack and try it one day with different weights and objects in it to really see......
I am a big fan of fanny packs for hiking and carrying camera gear. I also like one pretty well for carrying some stuff on the MTB on the trails. It keep the weight near your center of mass and moves with you. Back in the day I used to carry some heavy camera gear on technical trails and a fanny pack was a great way to go. I suspect I might go back to touring with one for more technical trails. That said I'll probably stick with a backpack for road touring or gravel roads.
An exception is one that is more of a waist wallet that hold my phone and wallet stuff. Amphipod makes a nice one of those. It is handy around town. I always used one when I was into trail running.
I also like the LowePro Sling pack for micro 4:3 camera gear, but wouldn't tour with it and do not even ride with it at all. Great for day hikes though.