A developing agent is a discriminating reducing agent. Thus HQ and Metol are developing agents and reducing agents. Stannous Chloride is a reducing agent but is non-discriminating and thus is a fogging agent but not a developing agent. Sodium Sulfide is a strong reducing agent and non-discriminating. It can act as a non-discriminating developer, a fogging agent or a reducing agent.
The Ilford paper contains an agent which will develop the Silver Halide when presented with an activator solution. Now, make of that what you wish, a reducing agent is present which will develop a brownish black image in alkali in the samples I tested. If it caused fog, then under normal conditions, the paper would fog.
It may be there as a preservative for all I know, but it meets my criteria. That is all I can say. I would not suggest using it in an activator due to the poor image quality. So, whatever it is, it is rather weak.