Layers pellets used to always have things like fish and bone meal, this would be why it was always to be kept away from ruminant feed.
All the time I have had chickens (only about 3 years) the feed does not have this in,and doesn't say on the label not to be fed to ruminants, so can be safely kept next to the sheep feed as the apha lady confirmed when she visited.
The reason you shouldn't let sheep eat layers pellets regularly is the high calcium level. Makes strong healthy egg shells but if not making shells it will solidify out in other places such as bladder stones.