The "4 hour" is doing a lot of work here.

Put another way, you need the gas turbines for the two week dunkelflaute (winter doldrums). Given that you have the turbines already, when are batteries cheaper than running the turbines for a few hours every evening?

A more interesting question than the cheapest 4 hour solution. I think that answer might also be batteries soon.

The point of the article is that a specific peaker technology (open-cycle gas turbine) is now less costly than a different peaker technology (batteries) that fills the same niche (short-term demand spikes).

Four hours isn't "doing a lot of work," it's the whole point of the article. It's not about dunkelflaute.

This; batteries are still ungodly expensive for seasonal or long-term storage.

And what happens if you need to satisfy peak demand for more than four hours at a time (and you will)? You still need some generators or overprovisoned batteries.