True that ruminants process fiber better than poultry. However, if the sprouts are fed out at the sprout stage, instead of holding them to the fodder stage, the amount of fiber would be greatly decreased. I feed out my sprouts before the grass blade has exited the monocot sheath. IMO, the fiber content at that stage would be minimal, while the nutrient level should actually be higher than it would be at the fodder stage. The day before I intend to feed my sprouts, they go on the window sill to "green up".
The best way to assess how a flock does with sprouts or fodder is to actually do it. Monitoring flock condition, as well as their fecal output seems appropriate no matter what feed you are using.