This is the same as Stoekler's two-bath.
In theory, a two-bath dev works well with most films. While in the A bath, the emulsion soaks up the developing agent with little or no developing going on. In this case, there is 5 grams of metol and 100 grams of sodium sulfite in bath A (very close, if not dead on, to D-23.); enough to do some developing. The B bath contains the alkaline to make the dev agent work faster..
The advantages to a two-bath are some compensation in the highlights as the developing agent gets used up quickly, and you are able to process two different kinds of film together.
In practice, this can be different. I've gone thru all of the two-bath formulas in Anchell's "The Darkroom Cookbook" and the only one I've stayed with is D2D. All of the others, including this one, did not develope the film enough. One reason could be that modern emulsions are not thick enough to soak up enough of bath A. I was advised to increase the metol by up to 50% and to lengthen the times.
Original times were 2-5 min. in A, (not very helpful) and 3 min. in B.
If you want to try some test rolls, I'd go to 7.5 grams of metol. I might also go to 4 min in A and up to 8 min in B. Those are the times that work for me with D2D.