I also agree with you. It is not a new thing that the price of Bitcoin will increase and decrease again. It is nothing but foolish to think that any other currency can take the place of Bitcoin if the price of Bitcoin decreases. So I think Bitcoin has never changed!
That is we called volatility, all crypto have that kind of market features and it never changes the looks of Bitcoin. But this is not the only thing to say that Bitcoin had never changed but OP is pointing out how the hardfork affects the marker position for Bitcoin. Eventually, there is nothing and that hardfork even tells that Bitcoin remains to be the king among crypto. And that also tells that Bitcoin is a unique coin created, nothing could ever be compared to.