Let me give you an example. Film "A" has 300 mg of gelatin per square foot and 300 mg of Silver Halide. Film "B" has 600 mg of gelatin and 300 mg of Silver Halide in the same area. Now, film "B" will absorb 2x more solution 1 than film "A" and therefore will have that much more to carry into solution 2. You therefore get more development with film "B".

In this case, film "B" might be an old film and "A" might be a modern film, as per Paul's example above. And so, you have to either accept thinner negatives from film "A" or adjust solution 1 or 2 for these new conditions.

The fact that you do not observe it may only mean that you have not done side by side comparisons and / or, you are getting less than optimum result.

For this very reason, divided B&W developers never were really commercialized by EK, Fuji or Ilford.

BTW, the Wikipedia article is incorrect. It implies that commercial processing is done with a 2 bath developer. This is not so.