The whole deal with 2 bath for the purposes of use on unknown films or getting the most from shadow details, is simply taking advantage of the fact that higher densities exhaust develop quicker that the lower densities. The first bath is the "developer bath", and the second one, having little or no developer, but still being alkaline, the second bath provides an environment for the carry-over first bath to keep developing the lower densities until complete developer exhaustion, and the higher densities will have ceased developing earlier because they have already exhausted their developer. Because the second bath is done with little or no agitation, can create areas on the film where developer distribution is uneven, causing mottle in some cases. But I will always contend that if 2 bath developer provided any real advantage, Kodak would have marketed one. But they knew that the tonal range of print paper is so much less than film, any advantage is mostly nullified anyway. On unknown films is where there's the greatest advantage. If you have Panatomic X and develop it as Plus X in a 2 bath, or Tri-X developed as Plus-X 2 bath, the former will be overdeveloped and the latter will be underdeveloped. But the 2-bath can better come to the rescue and provide a better chance of having a printable negative. on all.
If the argument is that there can be no value in using anything other than Kodak or Ilford chemistry, I would question that. f one takes HC-110 at low dilutions, it could be argued that all Kodak developers are of the same general type: fine-grain solvent developers. Kodak, at one time, made a Rodinal-like product, but no longer do. There is not that much diversity. They have no pyro developers, no true high-definition developers, no two-bath, no developers for document films. Until recently, there have not been many commercial pyro developers, at least in the modern era. But proponents of pyro say they have benefits that cannot be achieved with conventional commercial developers.
To say that if any of those other kinds of developers were any good, Kodak would have made them may miss the point. What Kodak decided to produce and invest R&D into was based on the potential for mass-market sales, not solely for artistic merit. Nowadays, the main use of analog materials is for fine art photography. But fine art photographers were a minor consideration in Kodak's decisions about developers. Their developers were primarily designed to meet the needs of commercial and industrial customers. D-76 was initially developed for the motion picture industry.
Steve Anchell says that D-76 became the best-selling developer, not because it was the best in all respects, but because it was promoted by mighty Kodak, it became a standard. Because it was a standard, Kodak feared purturbing customers by changing it, even though it had known drawbacks. We know Kodak was aware of drawbacks because Grant Haist, a Kodak employee, formulated an improved version: D-76H. They wanted to fix it, but couldn't. There are other improved versions as well. Now the best versions of D-76 may be the home-mixed ones. The success of D-76 caused Kodak to get locked into its formula, rather than improving it. So the fact that it was a big-time commercial product with the full power of EK behind it actually impeded the resolution of its problems rather than helping with them.
