While I have seen many times over that "sp-lodash-subset is a subset of lodash functions", I haven't been able to find anywhere a list of _exactly which functions are included_.
This page is blank: https://docs.microsoft.com/en-us/javascript/api/sp-lodash-subset
This page does not have any details either: https://www.npmjs.com/package/@microsoft/sp-lodash-subset
The only reference to it I can find in the main SPFx documentation is on the Toolchain page, where it just says, again:
Provides a custom bundle of lodash for use with the SharePoint Framework's module loader. To improve runtime performance, it only includes a subset of the most essential lodash functions.
But still no reference to which functions are included.
Even if the "documentation" is just a link back to the documentation on the lodash website, I think a definitive list of exactly which functions are included would be incredibly helpful.
(Currently the only way I know of to see what's included is doing "exploration via Intellisense" in a named import line, which is....annoying. And inefficient.)
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There's a known issue with the API doc generation on the site... they are working on that.
But the easiest and best way to see what's there is to look in the /node_modules/@Microsoft/sp-lodash-subset to see what's functions are listed there, specifically the index.d.ts file.

To see what each one does, refer to the lodash docs: https://lodash.com/docs/
Ah, I did not know they were listed out like that in that file. Thanks!.

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