The term uber-style is meaningless and just invented. The grid has some capacity to provide power. It can't supply any more so there would be no point in varying charges based on load. It can suply no more than it does. They do have one problem - sudden surges and time taken to get generators up and running. That is what Dinorwig is for but battery storage is being used more and more. If total wind we will need a lot of that. Probably not feasible so some greens will accept nuclear. Not the UK ones though.
You mention capacity, as in the ability to increase capacity on demand but with time lags. I get that but, seriously, sudden surges? When do we witness such surges? Don't they have software/algorithms that are pretty accurate at anticipating such surges? I fully appreciate that no algorithm is perfect.
The term Uber-style has now entered the lexicon. It is a reference to surge pricing. Demand increases, in theory supply should increase to meet demand but companies like Uber use it as an excuse to price gouge. Uber will inflate the price and take their 15%(?) commission, in the meantime, other firms will provide the same service at their regular price.
Simply providing more energy for kettles during the advert break for coronation street should be anticipated and not an excuse to increase costs. That is the way that tax dodging companies such as Uber operate.