Not necessarily true in all cases, or small herds.
My setup is the same as @Janet - free access to stalls 24/7/365.
My mini - who has his own stall & knows it - routinely goes in with the 16h Walker < Herd Boss.
They share hay until I dispense grain, then mini goes into his own stall. Finishes his grain, then goes back to Walker’s stall.
Even if Walker has not finished his grain, there’s no aggression besides the occasional flattened ear or sideye <- Walker to mini.
Mini never tries that with the 13h Hackney, though they get along fine turned out.
Hackney will make faces at the Walker, but only through the grille between stalls.
Walker largely ignores this insubordination, but on the very rare occasion, will leave his stall, “evict” the Hackney for a minute or two, then return to his own stall.
Never any biting, kicking or other violence, but the Message gets sent & received.
Years ago, a large boarding barn had a group they called The Retirees. All aged.
Some 10-15 horses routinely were turned out by opening door at the end of the aisle that led to their turnout, then opening their stall doors.
Group walked sedately down the aisle & into pasture.
”‹”‹”‹”‹”‹”‹”‹Process was reversed to bring them in, all filed down the aisle & back into their stalls.
