I... put politely, don't understand how manufacturers can make that claim, it depends on exogenous factors. That said, you're right, the newest turbines are impressive structures and more consistent at their job.

Also that said, andy_ppp is right, or will be soon. If you want to make a dent in our fossil fuel needs on a cold windless day, you'll have giant globs of excess energy on warm windy days, that is simply orders of magnitude more than any practically-costed battery can store. At that point, who cares if electrolysis is only 30% efficient?

Your margins care, since those are a factor of installation cost, marginal cost and energy lost due to round trip efficiency.

That 70% loss defines the lowest possible price difference between buy cheap power and sell expensive. Therefore any other smart consumer or storage has that margin to work against, to compete you out of the market. This is why batteries can work, in some cases. But it is a pure inefficiency that will find a minimum equilibrium.

For your understanding, capacity factor is one of the parameters which is under the control of the turbine designer. If you connect up a huge 200m turbine to a little 3kw generator you can get a practically 100% capacity factor but obviously it's not an optimal strategy given the costs.