Trust me, I know infinitely more about it than you do.
You said 'because of capacity on demand...'. This is, in fact, false. The thing that lets them control the performance and configuration of the machine is not 'capacity on demand', it is 'Licensed Internal Code Controlled Configuration.' The use of LIC CC also allows them to offer 'capacity on demand', but they are not the same thing, and LIC CC does not require COD. Also, notice the name of that facility, it should give you a clue as to what is actually licensed.
Having said that, I already explained why multiple performance levels are offered. Why would you pay (for hardware and software) for more performance than you need?