I often stand at the bottom of a creek on an incoming tide in my waders then move back with the tide so cup my hand over the chambers where an auto will be spitting out the spent shells to see then floating away!
Regards taking 3 shots the reality of shooting 3 pigeons is the last bird will be on the cusp of distance flying away so the vitals will not be showing and you will chip it, for me 2 on the deck is enough at a time.
With an auto you have only one option of choke where I use my marsh gun then the 1/4 - 1/2 option works very well
as I will have often have a 32gm 4 in the 1/4 and 36gm 3 in the 1/2 choke so the option to switch if a high straight line bird is belting down the creek. (not with an auto)
Also same with my pigeon/game/rough shooting 12b but cyl 1/4
Regarding rough shooting I was taught to walk with it broken then close and shoot as it is technically
safe being broken where an auto is not as is shows loaded.
Back to pigeon shooting or in a clay stand , you never see the likes of Andy Crow Gerwyn Jones G Digweed Richard Faulds in the hide with one, Geoff Garrod yes but on clays he use an ou (as I have scored on the charity events he comes to) also on driven days he uses an OU.
You cant bend an Auto stock like a piece of wood (cross over stock ) is a good example also they don't handle or balance as well as a OU/sbs.
Waiting out the high tide with no spent rounds floating off..