This is more akin to my forking the GitHub repo for MySQL and calling it MySQLCash (MCH, naturally). It doesn't change anything about the original; that only happens if the new asset wages an adoption campaign like BCH/BSV/Bwhatever, in which case the origin story is irrelevant.
And remember, the value of a chain is not simply its code. In fact, you can argue that the code is NOT important AT ALL to the value of a chain, for the very reason that it is entirely open. The chain's valuation comes from the network - and arguably the most important of those (at least in the short term) - the users who transact on the chain, and the miners whose hash power push the chain forward, will splinter.
When a chain splits, the miners must make a decision on what percentage of their finite hash power should be allocated to each fork.
I'm actually of the belief that this analogy is VERY good.