Sodium sulfite is sufficiently alkaline to release the Metol free base. Remember that D-23 works as a developer because the solution is still alkaline even after 7.5 g of metol have been added.
My objection was in the blanket claim that Metol will not dissolve in sulfite solutions. It WILL dissolve but at a slower rate. If it didn't then such developers as D-23 or D-76 could never be mixed no matter in what order the chemicals were dissolved for as soon as the sulfite was added the Metol base would precipitate out.