Thats not a limit in the sense of you cant build bigger MWH into...

Thats not a limit in the sense of you cant build bigger MWH into battery. it is however a cost optimization meaning they just dont.

batteries make money for jam money by providing grid services where their existing and potential to do stuff is whats paid for.

A battery can sit the part charged and basically instantly (in lay terms) do raise or lower. The overhead cost for being ready to do that is near zero. In order to be able to offer raise and Lower a FF power stations has to be running and consuming fuel generating costs.

batteries to do arbitrage have a cycle cost that is non trivial as batteries can only be charged and discharged a certain number of times before they wear out. Conversley they also have an age limit where failing to cycle them eventually also lets them die and wastes cycles they could have done and made profit from.

Tuning the size in MWH of the battery so it gets cycled often enough to make good use of the capital invested means we dont now and likely wont just keep making batteries bigger until the worst hardest problems are solved.
Long duration storage will be solved with technologies like PHS that dont just degrade so much over time causing such depreciation costs.

So there will be parts of producing zero emissions rid that will be solved by PHS, there will be parts (shorterm small MWH) solved by batteries, they are also good as they can be paced in the grid at the desired location (where desired means good for grid reliability) and dont have to be build where the suitable hill is.

Then eventually as we get real close to 100% and shut down the last of not the coal but the gas power plants we will probably use something with even better very long term storage characteristics. At some point, a smallish number of plants with 100+ hrs of storage capacity will be needed. things. Snowy 2.0 and BOTN wont I expect be quite enough, so will also make and storage hydrogen derived fuel.
That will be a quite and expensive way to get MWH, so, IMNSHO DYOR, it wont dominate things like K2H from one side just like batteries wont from the other.