There is no legal definition as to what constitutes bitcoin.
There doesn't need to be.
Any third party exchange or coinmarketcap can call cryptos whatever the fuck they want and idiots like yourself will believe the source of news.
They do so for the sake of clarification for their customers/viewers. If they started pretending SV or BCH was bitcoin, they'd lose traffic.
Find me any court ruling in any country who has declared the btc chain as bitcoin and I will shut up.
Irrelevant. Courts don't exclusively decide what is reality. Sorry your investment tanked.