yes,
having jeff clark and ned stuart overlap so closely was weird.especially given that they looked and acted exactly the same.they could have done something to differentiate the two characters but they didn't.
my guess about this is that roger davis had a contract and Spoiler:after jeff "disappeared" into the past the producers needed to create a role for him.
ned stuart was a pretty minor player.they could easily have hired a different actor for his few episodes so using davis must have been a cost-saving measure or a contractural obligation.