I guess you could say my little one fed on a schedule, although that was much more his choice than mine. From the very beginning DS ate every 90 minutes (I want to add in here that he was adopted and we're talking about bottlefeeding) day and night. If I tried to feed him at 70 or 80 minutes he'd refuse, turning his head, spitting out the nipple. If I wasn't ready at precisely 90 minutes he'd become hysterical, and so our life became pretty scheduled. If we were at the park and it had been 80 minutes I'd wait another 10 so I could feed him before leaving and not have to stop 1/2 way home. If he had a doctor's appointment that started at 4 and I knew he'd want to eat at 3:50 we'd get there at 3:40 so I could feed him more easily.
If he started crying and it wasn't right around 90 minutes I wouldn't think to offer the bottle, but first would try changing his diaper, or walking him, or putting him to sleep. If he kept crying I'd eventually think of the bottle but I don't think it ever worked once. On the other hand, at the magic moment I'd offer a bottle at the slightest stir, and sure enough he'd slurp it down.
I can imagine a mother who is on the fence about scheduling having a child like mine and thinking that her scheduling was "working", as long as she was smart enough to come up with a 90 minute schedule instead of 2 or 3 or however many hours the book says.
As far as adults eating whenever they're hungry, that's not my world. I eat right before I leave for work, even though I'm not hungry then, because I know I'll be hungry in an hour if I don't. Then, since I'm a teacher, I don't eat until my lunch break which is always the same time. Some days I'm starving at 10 and some days I think "I"m not hungry but I'd better eat something because my next opportunity will be when I get home around 7:00.