Dektol vs D-72

According to this, http://www.flickr.com/photos/camerawiki/5562506733/ Kodak Dektol is based on D-72, but stays clearer for longer, has been improved to provide a greater working capacity and a longer shelf life. How does it differ from D-72?

That being a 65 year old ad, things have changed some. But they are the same with the addition of a sequestering agent. See (there was a url link here which no longer exists)
Should answer your question.

I guessed that the sequestering agent would help keep the solution clearer and may be help extend the shelf life of the stock solution, but I don't see how it can increase the working capacity.
It doesn't matter much, I was just curious how Dektol was different from D-72. Thanks for the link trexx.
From my Kodak Formulary, D-52 is similar to Kodak Selectol and D-165 is similar to Selectol-Soft.