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major analogy time. seeing as the OP brought up the "empire" analogy. legs start with that
imagine in 2009 there was a british empire. that had one currency, that everyone on many continents agreed was one currency network/medium of exchange called the dollar for years one network. many communities, many maintainers of record and many rule lobbyists
There really is no need for coming up with forced analogies and creative ideas like bilateral split etc etc. Only one Bitcoin is needed. If you want to trade or buy it, then go for the BTC ticker.
This constant distraction about bitcoin being a well-defined, objective idea that should only follow the whitepaper as a bible is absurd. The community project that was handed down by Satoshi has SegWit implemented in it's current form.
It is the network, the community and the individuals world over who value and identify the historical transaction database associated with the BTC chain with Bitcoin Core being the main client/ software. That is sufficient to identify Bitcoin.
Doesn't change the fact that Bitcoin Cash is an alt-coin and these marketing tactics are just a dirty businessman's game. These people have done everything from misleading newbies through their owned platforms to manipulatively pumping it during crucial events.
Today if somebody were to start another chain fully compliant with the original code devoid of all the BIPs and start calling it the the "Bitcoin Vintage", it won't be bitcoin. Bitcoin Is. That's it.