If the food is outside they will go out when they get hungry.
If the food is in the coop it should not be .
It is normal for hens to fill their crops and go sit in the coop to dry out for a couple of hours if it is rainy .
Don't know why feed shouldn't be in the coop. Been keeping it there for nigh on 20+ yrs now.
Most UK domestic coops are not big enough , the food attracts vermin at night and the hens might not bother to go outside !
Alway exceptions to the rule , huge coops and countries where the hens are better of inside during the winter.
How big is your coop?
10X12 I don't leave feed in the coop overnight, as I feed a daily ration and just enough that they clean it all up before nightfall. Keeps rodents from becoming a problem, no matter the size of the coop. If you leave it outside, the wild birds dip into it and bring along whatever mites and diseases they may be carrying along, so it's six of one, half dozen of the other about leaving it out or in~birds and squirrels outside, mice inside.
Since I just feed once a day, the hens go out looking for food outdoors until they get that food, so just feeding a daily ration may take care of all those problems of feeding inside the coop. It's easy, it saves money from less feed waste, it eliminates the pest factor.