@iointerrupt point taken that the model is complicated (and just a model). So maybe something about the multiple compartments offgassing simultaneously is confusing me. But, in the example that you gave:
Wouldn't we expect that the faster compartment would be offgassing, well, faster than the middle compartment? And so you could never have a situation where the diver is remaining at a constant depth, and first the middle compartment is controlling, and then a few minutes later the faster compartment is controlling? In my mind, this is a contradiction, but again, maybe I'm missing something obviousPurely in theory, if a middle compartment is leading, but off-gasses enough to make a fast compartment leading, the rate of change could be as the example shows, slower then faster.