"Therefore, they state that sulfite addition accelerates HQ and Metol development."
I saw no such statement. I saw no place where they even implied such a statement. They did no tests that could be interpreted in that way. Those who produced the graph I sent did not present any evidence that HQ adds to the development by Metol, either synergistacally or simply. They did present evidence that sulfite accelerates development by Metol without HQ. I see no place where these researchers stated that sulfite accelerates HQ and Metol development.

The graph clearly shows that there is not even an additive let alone superadditive effect between Elon and hydroquinone without the presence of either a sulfite or ascorbic acid. The activity of Elon is approximately doubled by the addition of either sulfite or ascorbate.

My own experiments, which anyone can repeat, show that either sulfite or ascorbate at the same molar concentration stimulate the same degree of superadditivity between Metol and HQ, and at the same pH. The pH of a 10 g/l borax solution is bountifully sufficient for either an MQS or an MQC developer. The molar concentration of S need only be the same as that of the C. If you do not want stain, you can substitute as much sodium ascorbate as you want for the Q.

At any rate, I learned what I set out to learn. Ascorbic acid, which is soluble in glycol or TEA, can be substituted for sulfite in such developers as the Pyrocat series and also in PMK in quite small amounts. There is no loss of activity if, OTH, sodium ascorbate is substituted for hydroquinone in the usual MQ or PQ developers.

I doubt that Kodak had much interest in creating or promoting staining developers in glycol solution.