When you think about things like this, it is really important to realize that one of the components of the ISO film speed standard (and before it the ASA and DIN standards) is contrast.
So Ilford and Kodak and others can decide to design a film that meets the ISO specification in one way, while minimizing contrast in another way.
If you want to really start wondering about these things, consider why Kodak recommends the same development time for T-Max 400, whether you use an EI of 400 or an EI 800.
Because in Kodak's opinion, while an increased development time may have the benefit of increasing contrast in the shadows and near shadows, that benefit will be outweighed by the reduction in the quality of how the highlights are recorded.
The contrast compromises built into Ilford 3200 are designed to maintain the quality of the highlights when the development is increased to benefit the shadows and near-shadows.