There is some quite through justification for the chilling time/temp requirements water v.s. air chill---I was a poultry gal for quite some time, but man my brain does miss it!!!
A--water chillers are virtual cesspools of bacteria (as they are shed from the carcasses once they enter the chiller----new systems use PAA, old systems chlorine MAYBE) if the time/temps are not followed, you'll actually get exponential bacteria growth
B--water chillers do not do a very good job----water is a horrible medium for adding/removing heat....the heat exchange calculations are not good, then you add hot carcasses to it, and you've now got water chillers that may not be chilling
C--unlike red meat which is not harmed by "rot" there is a VERY small window with fresh dressed poultry prior to chilling....the bacteria load tends to be really high by the nature of the process, red meat can be safely trimmed.
D-water chilling doesn't allow for a rapid cold crust to form......temperature changes is actually quite slow for the first 2 hours (as per data logger data) so you've still got bacteria growth
E-carcasses are rubbing against each other slowing the heat transfer even more
F-salt is added to artificially lower the chiller water, but it impedes heat transfer (it also has a nasty habit of breaking cell walls giving you limp poultry that won't crisp up no matter what you do)
Air chill removes heat AND humidity from the surface of the carcass so rapidly, that the bacteria cells are essentially frozen in time.........the carcass is also wide open where it was eviscerated so you've heat being rapidly removed from the surface and the cavity. So there is no chance (barring mechanical issues of course) of the carcasses warming, the bacteria growth cannot occur OR occurs at an acceptable level
CFIA has water make up ratios (amount of fresh cold water) that needs to be added for each carcass at X weight and X temperature
Where I was, we could air chill small birds from 90F to 14F in 90 minutes in the blast freezer