These are sold as £x/month to include handset and airtime, with a minimum contract period. There isn't a separate figure for the handset to be paid off, and any assumption that if it's a 24mo contract then after 24mo the handset is paid off is flawed; yes that's often the case but also it's off cheaper to get a 24mo contract for the phone you want (and throw away the SIM) than it is to buy the phone outright, which could be funded by the expectation that enough customers will continue to pay out of contract that the you cover the costs in aggregate if not always individually.
If the case succeeds, as is usually the case with such things, the outcome will be that the best deals will be pulled and the savvy consumer will be penalised to protect the lazy customer.
Anyone wanting to get the phone separately from the airtime has had that option for as long as I can remember. I've been on the same contract for over a decade with several phones in that time (often second hand ones). It's a competitive market and individuals need to be free to make their own choices, including choices which might not be in their interest.