system.dataset.toDataset(headers, data) vs system.dataset.toDataSet(headers, data)

I am trying to migrate to 8.3, and working on updating the depreciated functions, the toDataset() function is confusing me, in the documentation it is toDataSet with Capital D and Capital S while in the designer's suggestion it is with Small S

Which one is right and which one is wrong?

toDataSet is the legacy form, deprecated precisely because the capitalization is confusing. It's existed in that form since its creation.
toDataset is the preferred form, new in 8.3.

The two functions do exactly the same thing. The deprecation is just to fix the nuisance capitalization. In 2027.2, our next major version, toDataSet will be hidden, but still work.