You can find a clear explaination in the wikipeadia article for hard fork, ref.10
Here is the IRS .pdf:
https://www.irs.gov/pub/irs-drop/rr-19-24.pdf
There is actually an easy test, it wasn't a split because the history of hf23 will not diverge.
In theory people could run hf22, but it is not the consensus, so oddly it would be the new asset.
Nice, thanks.