The only difference I can see from the MSDS for Microdol-X and Perceptol, is that Kodak list boric oxide (B2O3) as a component. Both developers list sodium chloride as constituents.

A former Kodak pundit has mentioned on a popular photo-forum, that Kodak encapsulate the developing agents with a special coating to prevent them from reacting with the other constituents in the single-powder compounds.

I am wondering if that special component is the boric oxide (boric anhydride) that Kodak mention in their MSDS's.

Ilford do similar to their P.Q. powder developers by adding a pinch of sodium metabisuphite in Part 'A' of Microphen and Bromophen, but not in ID-11 or Perceptol, as Metol is already slightly acidic.

Ilford information sheet P 10.5 FINE GRAIN DEVELOPMENT: Shows that ID-11 and ID-2 can be modified to produce finer grain by adding ammonium-chloride. Use 40 grams for each litre of stock ID-11 and 10 grams for each litre of working strength ID-2 (1+2).