My Senior grain is pelleted and has no sweet feed in it. It was just a suggestion. I don't think the blanket statement of "Don't feed him Senior" feed is correct.
My other horses get Aussie Logic's Kool and Kalm. It helps to keep my hot headed horse a little more level headed and gives my collicky horse better digestion. We will be starting the Rescue horse on it as soon as he finishes his last bag of Equine Senior.
I really believe it's about finding what works for your horse. If he was always on hay, what's the problem with staying with that and fortifying with supplements if needed?