Michael, in a 1930's Agfa Patent they were using a wetting agent sodium dibutyl-napthalene-a(alpha)sulphonate in a p-Aminophenol developer to overcome uneven development. This also has anti-oxidant properties.
It's known that Sodium benzenesulfonate was used by Orwo & Foma in R-09 from Soviet and Polish publications. Kodak, Fuji and Ilford all have Patents relating to Sodium benzenesulfonate or it's derivatives, citing them as anti-oxidants and wetting agents. These componds aren't developing agents.
There's an issue of what is or isn't a developing agent, a compound might have an ability to develop a very weak image (in an alkali solution), or it might provide an additive effect to a developing agent. Sodium benzenesulfonate or it's derivatives have been used alongside colour developing agents to increase solubility and promote more efficient development.