It may very well be a high pH developer, but the ratio of hydroxide to Metol is such that there is just enough of each to form the sodium salt of metol. I don't have a pH meter, but I wouldn't expect the working pH to be much different from that of a similar molar concentration of sodium carbonate. Maybe someone with the proper equipment who knows how to use it can measure the pH of the concentrate and of several different concentrations of working solution just for fun. Of course, if you were to bubble sulfur dioxide gas through a sodium hydroxide solution, you would eventually reach a solution of sodium sullfite in water, which is not nearly as alkaline as the original hydroxide solution. The old rough test is to see whether the solution feels soapy. I haven't paid much attention to that. It would not be good for one with Metol allergy to try.